I actually pay to REMOVE ads from my forum. i don't like them, and i'm not looking to earn money from ads. my forum does get over 100,000 clicks a month. i added a counter back in august, and already over 200,000.
when you remove ads on PB's server, you pay $7 for 50,000 page views, and i have it set so Guests see the "ads" and don't use up the pageviews`... and by the 3rd week, just from members using the forum's pageviews, i have to purchase more credits by then.
so i get plenty of clicks, but not interested in using those services. the turn around isn't going to go in your favor.
Across my websites anywhere between $600-$1500 a month (approx $1000 on average) - that is from a mixture of Adsense, Adbrite, bidvertiser, matched, money4banners and private cells
i am like sbfc93 i don't run forums for money. I run them because I either want to help others or bring others together. I can get a job to make money. Forums are just a "hobby" for me you could say.