Michael Z, you're right. Part of it I suppose is who is making the charges. If it's a high-level government or party official who is saying something unsubstantiated, it's more likely to be reported based on the fact that that person is saying it.
The real problem I see is that, with the internet's presence growing, virtually everybody with a computer - ranging from high-profile commentators like Drudge through to, say, a 12-year old schoolgirl from Pittsburgh - will be able to post allegations about prominent figures (whether it's politicians, rock stars, sports personalities, etc) for all the world to see.
Even though there are of course legal powers to stop this, for example by enforcing an injunction, allegations often stick, no matter how unfounded. And this is where the crux lies: if journalists are going to pick up any allegation which happens to be circulating they could effectively destroy someone's career for no good reason. Of course, the media, namely the so-called gutter press, are doing it right now, and have done so for quite some time, which is quite unfortunate. Oh well, I guess I'm not really addressing any specific points you've made, I'm just thinking out loud now.
You're right in the sense that there may be some grey areas with regards to context and who is making the allegations, but I'm sure we've agreed on the basic principle here.
