About 10 000 to 15 000 unique visitors (1ip/24h) per day with half a dozen sites. There's room for improvement, but the key is traffic, my webhosting is ok, it can take much more before crying, it's just google not sending enough people
Last year for a good 6 months it was wonderful, well over $100 a day with mainly one site, but the traffic died off from one day to the next because google decided so. The traffic from other sources is about 10%, the rest was from Google. So I built up traffic again but this time spread over several sites.
For instance I started a french digg-like back in september, after the traffic to my other site died off, now it's earning about $25 a day on average, and just one month ago I released the english version (in my signature) and my main activity since is to build traffic and membership for this one. I find it much harder than the french one, I guess because there are so many failed digg-like that people only trust established ones, and mine still has no PageRank (next PR update is beginning of july) but in a few months I'm sure shetoldme.com will become my main earner, because it has potential, Google willing of course