Its a valid question, and in fact I'm surprised only that it hasn't been asked earlier. However, the answer is rather complicated, so bear with me!
First, a quick answer -- yes, there have certainly been a number of (sometimes very aggressive) expressions of interest in me from Mosuo women. In fact, it rather intimidated me at first, I had no idea how to react; I'm used to the "typical" Chinese woman who will be quite passive and quiet, and suddenly I had women who were very actively pursuing me.
As I've mentioned elsewhere, Lugu Lake has become popular as a "sex tourist" destination, with lots of outsiders (both Chinese and foreigners) going there simply with the intention of having sex with a Mosuo woman. This is something that most of the Mosuo themselves resent very deeply, and I wanted to be very cautious that I not be perceived as being like that. Therefore, for my first year, I very deliberately stayed away from any sexual relationships with local women. This helped cement my reputation as someone who was there with a sincere desire to help the Mosuo -- not just as an excuse to bed the local women.
However, things eventually reached a point that I had not anticipated; there were several Mosuo women with whom I really was quite close, and who had all expressed interest in me. I had consistently said no. But suddenly, the Mosuo leaders in my organization started asking me why this was...didn't I like Mosuo women? Did I think they were dirty? Unattractive? To them, it was incomprehensible that I would be A) available, B) attracted to a woman, and C) have that woman attracted to me...but do nothing about it. The only reason that they could see was that I didn't really like the Mosuo. Rather ironically, a decision that I had made in order to demonstrate a sincere respect for their culture ended up being interpreted as a dislike of them!
I've developed a very close and open relationship with a few of the key Mosuo leaders, so sat down and had a long talk with them about this. I explained my motivations, and my reasons. And I asked them how it would affect my reputation and image in the area if I did begin having 'walking marriages' with the local women.
The response from every person I talked with was the same...that I had done the right thing by abstaining when I first came. They said everyone had been watching me, and if I'd started having sex with local women right away, it could have damaged my reputation. But now, it was an established fact in everyone's minds that I was there out of a desire to help them, that I wasn't just some kind of sex tourist.
But while I had embraced Mosuo culture in many different ways -- getting a Mosuo name, beginning to learn the language, participating in major festivals, etc. -- the fact that I had apparently rejected so many Mosuo women remained something of a barrier; and if I wanted to really be accepted by the Mosuo, I needed to be seen as participating in all aspects of the Mosuo culture.
Now, when I explain this, it seems almost ludicrous...a single, heterosexual male, with numerous attractive women actively chasing him, who has to be pushed into actually agreeing to do so. However, the answer is that yes, I have begun a "walking marriage" relationship with one Mosuo woman. It seems really bizarre from an outside perspective...when I went to visit my "Mosuo family", I would stay in their home. But when night came, I would "sneak" out the door, go to my partner's home, and climb in her window, to spend the night with her. The first time I did this, I had no idea what to do, and was afraid of embarrassing myself and everyone else; but one of my 'brothers' appeared at just the right time, congratulated me on finally becoming a "real Mosuo", and then showed me how to get out of the house, and how to get into the other house. (By the way, the woman in question has since moved to the main Lugu Lake tourist area, and has her own small apartment, so I no longer need to sneak over at night; I can just live with her when I'm there).
The first time, I was still afraid that there would be something of a negative perception of my actions, but this proved not to be the case. As my friends had told me, this basically cemented my position within the community, I was now "one of them".
I mentioned earlier that the Mosuo engage in "serial monogamy"; in my relationship with this Mosuo woman, neither of us will have other lovers (even though we really don't see each other very often). So long as we're happy with the relationship, it continues. If one (or both) of us decides it is no longer working, for any reason, we will end it. There are no expectations beyond that.
In truth, I've found this a wonderful relationship. She is a very intelligent and active person, a delight to be with. And whereas most of the time in China I have to worry that a woman who shows interest in me may just be after my money, in this case that isn't a worry at all -- since in the Mosuo culture, our property would always be kept separate, and she would never have any claim on it.
The big problem I have in this regard is not with the Mosuo, but with outsiders, when I explain this. In particular, it is almost inevitable that some women will start accusing me of simply "living a man's ultimate dream", sex without any responsibility, and of taking advantage of local women's naivety just to fulfill my own physical needs/drives. Or men who, upon hearing this, declare that they want to go there and get a Mosuo girlfriend too (without making any real investment in time or energy in the Mosuo community first).
The Mosuo perspective on relationships is radically different from that of most other cultures; whatever I do, it is inevitable that it will be viewed negatively by one side or the other. If I try to maintain a Western judeo-Christian form of morality, the Mosuo will see me as rejecting their culture. If I embrace the Mosuo culture, with all its practices, then I am perceived by many outsiders as exploiting them, of taking advantage of local women.
So, to clarify my own position -- I have engaged in only one "walking marriage", which now is a little over one year old. My partner is far from 'naive', in fact she's a very intelligent woman, who actively hunted me for more than a year (and if I'd resisted much longer, she may well have abducted me). We have a great relationship with each other, which is recognized and respected by the rest of the Mosuo community, including her family. I waited more than a year before getting into such a relationship, and did so only at the urging of close Mosuo friends.
Whatever judgments others may have, I am confident that I've done the right thing.