Perhaps the latter problem is what you would term spam. And you’re right, it definately needs to be thought about since, in the ubiquitous microformat future you are imagining, this will happen all all the time quite innocently when different event sites talk about the same event for example. In the uppercase Semantic Web utopia you might show this by all referring to a common URI for the event. You can do sort of the same thing with the url element of a hEvent if it happens to have a canonical URL. With other microformats it’s not so clear how to do this.

The first two issues, of false information in microformats, stem from their “describe your own stuff” mentality that is inherited in part from the Semantic Web. In fact, they’re more committed to it than the SW since they really do have to be embedded in content and don’t have a general way for referring. I’ve thought about this a good bit and I think there’s another layer that has to be created, either in combination with microformats or subsuming their utility, in order to overcome it. What if people could mark up content created by others. It’s del.icio.us tags vs rel=tag. Which do you trust more? There’s an old Clay Shirky post that I keep coming back to whenever I think about these things.

I have some practical experience in dealing with microformats but it’s limited so I’m definately interested to hear what others have to say on the potential hurdles to the coming uF proliferation.