I would say it is a near certainty. Separate from the high profile hucksters like Sylvia Browne et al, there are many people who, like you, honestly believe in their own abilities. Their belief gets (mistakenly) buttressed not only by the easy-to-garner positive feedback of their sitters but by the fact that many are naturally gifted at observation, even if they don't realize it. I suspect you had honed your own skills in that direction.
Further, sometimes they use them in helpful ways. There are people who are moderately or severely troubled who would not under any circumstance seek counseling but who would and do seek out what they see as spiritual help. The honest and benevolent though misguided readers such as you were oftentimes serve as a "poor man's counselor."
Hit the nail on the head there. I can say honestly that it was not malice. I genuinely was deluded and this wasn't helped by the superstition around me. I am certain that I was helped by my observational skills. The one thing that I am thankful for is that the only people that got involved with my "mediumship" were my parents and a couple of friends - and I never sought money. It was simply "x is happy where s/he is now" and making vague statements. To be honest, most of it was about me "talking" (telepathically!) to the dead and holding a "conversation" with them. It was rare that I would ever do a "sitting" and I only did that twice.
To put it this way, I think that I was bored and my brain started to write a soap opera where the ghosties were characters and I was a character/director as well. When I got bored and tuned out of whatever was going on, I would daydream. Fundamentally that's what it was I suspect - just a vivid daydream. It only happened when I was unoccupied or bored that the "spirits" would appear in my "mind's eye" and superimpose themselves like an etheral chromakey on wherever I was at the time. And my brain would invent dialogue and actions that they would perform. The funny thing is that the spirits were all like me. I suppose at the end of it I was a bit like Walter Mitty with split personality disorder
Did I do any harm? I honestly don't know. I did peddle woo and get others involved in my delusions so that could be construed as harm. In my defence I wasn't concious of perpetrating what is fundamentally a fraud. I did honestly believe that I could talk to the dead.