Well, sort of. Greg has a post about how it seems that lefty causes don't seem to be spending much money advertising on lefty sites (you know, like this one). I suppose the real question is - what's the purpose of advertising? If you're making an issue ad, like Move On, and trying to get your message out to a general audience and gain a few converts, then hitting general audience media is probably the right idea. However, if you're trying to rally the troops or do fundraising for a particular cause, then advertising on a site like this is probably the right thing to do. Lefty bloggers, or places like Cursor or Buzzflash, reach a pretty targeted demographic. It's gotta be cheaper than direct mail (I have no idea if Cursor or Buzzflash want or have solicited advertising).