Certainly blog posting is somewhat useful, but give feedback directly to the organizer. Assuming that the blog post alone was intended to fill that role, I'd suggest a direct email or perhaps even phone call with the organizers to talk one on one.

As an organizer who just put my first event (indieconf) on last year, and am planning my second iteration, honest feedback is golden. I had a few people who shot from the hip (thanks!), and I'm doing what I can to address those points this time around, but they were mostly minor points. I'm left thinking either no one really cared all that much, or it really was so amazing there's nothing to improve on - I don't think either extreme is true though.

I learned I did something poorly, and am trying to rectify it - getting feedback about particular sessions. Almost all the comment cards given out after the sessions were good or great - a few neutral - but less than a handful that were bad reviews. I initially thought "wow, we did awesome". I then realized people who'd left a session because it wasn't meeting their needs were not filling out the cards in the first place(!). Any ideas about how to collect that sort of feedback, short of specifically asking people to come find me or leave a note at the front desk about egregiously bad experiences? I've noticed people tend to bottle things up at an event, then blog about things later when there's absolutely no chance of fixing anything.