I've had the same thought running around my head since putting the TwitApps domain names up for sale yesterday... would people pay for it?
The reason I shut it down is because it no longer held any interest for me, but that would change if I could get some meaningful revenue from it. I know a lot of people really liked the services, and a number of people have said they would be happy to pay for it, so I think it's worth gauging the level of interest out there.
So, my proposal is that I get version 2 finished and put the site back up. I charge a monthly fee, let's say a fiver for argument's sake, and that gives you access to all the tools on the site (currently Replies and Follows). Existing subscribers would automatically get access to new tools I develop for the site.
Please give me your thoughts about this. If there's enough interest (enough to pay for the hosting and my time) I'll bring it back, better than ever!