why not? imagine this: you have a post about a new car lotery, 10.000 fro free. user gets in, see's an ad about the "car lotery" and clicks on ad. quite simple in fact, not usual, but simple. btw, my CTR never drops from 30-40%. Its a solid niche site and user wants to/needs to click on ads... A good one.
It all depends on site's niche. A forum its a low ctr niche, but a loan or health site can go up to highest ctr's.
just off topic grg I scrolled up and looked at your avatar and I thought o crap my computer froze again any way forums get a low amount of clicks because they usually have a add on every page or thats my theory