Only forward information where the original sourc is credible-- ie. you can assume that they did the necessary fact-checking and gave a reasonable description of the facts, because their credibility is at stake.
In this case, people took it somewhat seriously because it had "Green" party sourcing, which is why the other parts of the Greens jumped on it, because they knew their credibility was at stake.
One reason the "best of media" is a bit overblown is that you always need central sources of information, not because grassroots info sources don't matter, but because centralized sources have enough broad interests that they need to protect their credibility. The Indymedia idea is great taken to a certain extent (and large handfuls of salt on individual news items) but has to deal with the bottom-line problem of maintaining credibility in its information.
Not that established media don't lie, but they lie within certain known parameters of bias. We can real the best mainstream sources of info (WALL STREET JOURNAL, THE ECONOMIST, etc.) and take their basic facts relatively seriously as long as we mentally adjust for the bias in interpretation.
The problem with unknown sources is both the parameters of their bias and whether they may be flat-out making things up is often impossible to know. Thus we get stories of Israelis failing to show up to work on S11 and stories of CNN using old footage of cheering Palestinians.
-- Nathan Newman