Dunno. I keep holding out hope that ads can eventually be a substantial revenue stream. Not the majority of revenue, but substantial.
Actually, when the DC check arrives for August's ads (3 months hence <groan>), it'll be more than enough to keep me in smokes for a month.
I'm curious about your theory, though. Don't think I'm willing to shut the ads off long enough to really make for a valid test of your theory, though. I could see shutting them off for a week (at least while we're still exclusively using agencies), and when we start delivering ads inhouse rather than via agency, only show those ads. So, if we have total campaigns amounting to, say, 10,000 impressions per day, only 10k impressions would get ads and the rest just wouldn't.
Lemme ponder on it.
Edit: Also, I'm kinda curious what the impact would be on server-loading. A pretty substantial delay is introduced by those ads. A delay during which our servers aren't getting hit.
Speaking of delays, though, maybe some folks don't realize just how fast this site is when there're no ads. If they knew, maybe more would subscribe just to always have that kind of speed?