Mostly at weekend I look for new blogs and interesting topics and post/reply a comment on some of them.
In a lot of cases my comment is then recognized as spam and I'm threaded like a spambot.
It happens on a lot of different blogs. Since some weeks I practice it in that way that every time when a comment of me is recognized as spam I contact the webmasters and ask him "why".
When they look at my comment they also don't know why because it's a regular comment.
In former times I found akismet useful but nowadays its a pain because I now see it with the eyes of a reader and not just as a webmaster. I slowly loose the pleasure to comment on blogs.
Every webmaster should think about that if he or she wants to loose readers because of that.