It seems extremely obvious to me that if you don't want irrelevant or inappropriate ads, Jude, then you should surely be accepting ads only from hi-fi firms, not from 3rd-party general ad agencies or whatever. 3rd-party ad agencies are simply not at all motivated to limit or censor what ads they serve. They have a catalogue of clients on their books, all of whom they wish to make a commission from.
You can keep asking for screenshots of inappropriate ads from head-fi members, ad-infinitum, or you can simply remove this new stream of ads altogether and ensure, in one fell swoop, that ads on head-fi are from hi-fi companies only. You'll have a huge workload trying to keep on top of the endless stream of inappropriate ads which the ad agency inevitably serves to the site, regardless of your requests for discretion.
But I suspect you might, perhaps, prefer the revenue from accidental clicks by increasingly-vexed head-fi members. I hope I'm wrong about this, and I shall wait and watch, with interest, what action you take, but in the longrun, if it continues, the good thing you have going with this very busy & successful website of yours is going to come tumbling down because, as has already been implied by others, the membership is going to simply ad-block every ad on the site, by using ad-blocking browser plug-ins.
If that happens, your existing hi-fi sponsors will probably end up pulling out and then one may only speculate on how the site will support itself.
I hope that doesn't come to pass, and I therefore hope you succeed in finding a pragmatic solution soon. Perhaps some of the members with experience in such matters will chip in, here, too.
Edited by Mython - 4/30/13 at 5:51pm