I was going to bring this up to the arbitrators, but it seems to be a general principle of wider interest, so I'm bringing it up here instead:
The current arbitration case, [[Wikipedia:Matter of Theresa knott and Mr-Natural-Health]], has turned up some evidence that Mr. Natural Health has participated in a good deal of flame-warring and whatnot on Usenet, and has in some newsgroups been considered a "troll" and general trouble-maker, at least by some people. There is currently disagreement over whether this should be taken into account, or considered relevant at all. See that page's edit history and talk page for more.
Off the top of my head, pros of taking it into account include an ability to avoid dealing with known trolls and troublemakers (we don't wait for someone to troll Wikipedia extensively if they've already trolled a dozen forums and sites before). Cons include possibly carrying over unwarranted persecution from other forums to Wikipedia (we can't always be sure of who the people making accusations are, and most of us aren't familiar with the context and climate of these non-Wikipedia forums).
Comments can go here on the mailing list or on the talk page referenced above. This seems like a general principle we ("we" here being "Wikipedians") should decide on, not just for this particular case.
-Mark