Forums always have a low CTR. Unless your part of a forum, i would advise not using adsense on one. Health previously did well with adsense but is now becoming victim to smart pricing. The only niche that i know about that hasn't been affected by smart pricing is finance. But im sure that will soon be affected by smart pricing. But the problem lies with bad advertisers, which google will eventually clear out leading to minimal smart pricing.
totally different experience and oppinion ! i have 5 forums 4 have ecpm between 15 and 20 $ only 1 below 10$ 4 forums have CTR between 5 and 10% 1 forum more than 10% (my site wide average is BOTH (ecpm/ctr) in 2 digits its NEVER a problem of forum its a problem of forum admin doing TOTALLY layout of forum and totally wrong adsense formats and ad placements!!! most forum have similar to DP forum hence TOTALLY deoptimized adsense change templates change colors change placements and you get solid forum revenue
If you make site which gets lots of traffic, then you would make money. Traffic = Money (thats the only secret) Ani
"high traffic" is relative i have more traffic on my forums than most ppl on an entire site, however i have several other more important sections on my site totaling some 200+GB traffic-volume / m
Forum users aren't likely to click ads unless you have a specific niche.. I noticed that back when I used adsense on my forum. Sites that do well with Adsense are high quality informative websites.