Very misleading. I think you'll find that if you were to look at the breakdown of murders, it's incredibly rare for friends to murder friends. When statistics refer to "people who know each other", it's almost always partners, ex-partners, or jealous lovers (or jealous people who had fantasised about being the victim's lover, and who might perhaps have been spurned by the victim).
In a far smaller amount of "known to the victim" cases, the perpetrator is a family member (mothers or fathers killing children, adult children killing parents, sibling murder over jealousy or inheritance). And an even smaller bracket would include an acquaintance of the same sex killing someone over rivalry towards the same third person (e.g. love triangles, or one person's jealousy over another person's partner). Lastly, of course, people acquainted with each other can kill each other over significant matters of money or status - the classic example of which might be the right to "own" a patch of turf for drug-dealing, or - amongst young males in particular - for leadership of the gang or group.
But I'd suggest that it's only in a vanishingly small number of murder cases that friends kill friends without one of these factors being present. In the Kercher case, Knox and Meredith were unrelated, had known each other for all of six weeks, and were not known to be competing for the same male. Similarly, Sollecito barely knew Meredith, had just started what appeared to be a fulfilling and exciting relationship with Knox, and had exhibited no prior history of having a sexual interest in Meredith. Guede, on the other hand, was not in a relationship with a woman, by all accounts had difficulty in forming relationships with women, and had (by all accounts) a reputation for hassling women in an inappropriate and sexually-suggestive manner.
