I just read this on a Facebook group's discussion board, but have yet to verify* whether or not it is true:

If anyone is on twitter, set your location to Tehran and your time zone to GMT +3.30. "Security" forces are hunting for people blogging about the current abuses of pro-democracy protesters using location/timezone searches. The more people at this location, the more of a logjam it creates for forces trying to shut Iranians' access to the internet down. Cut & paste & pass it on.

Makes sense to me, and I guess for now it doesn't hurt to try.   

Please help spread the word on Facebook, too.

 *tweeted @ev @nk @biz @rejon @wired @palafo @davewiner @techcrunch