Some people are wondering what's the catch with offering the Social Alerter for free. The short answer: there is no catch. The long answer...
The idea for Social Alerter evolved over many months. Initially it was a very different personal project meant to just keep an eye on Digg and del.icio.us. Then the idea of creating real-time alerts crystalized, helped by seeing many sites go down when the Digg traffic hit. Some of those sites that crashed under the load were friends' sites. In the end I realized that most webmasters are too busy to constantly keep an eye on their hit counters or analytics packages and an alerting service would be very helpful. A straw poll confirmed that and that was that!
Why free? Two reasons: all my other online tools have been free historically, and using the APIs of the social bookmarking and news services precludes commercial usage. The latter is very important as I do not enjoy getting banned and stuff ;)
So who pays for this? Right now it's being funded from the income of my other sites. If and when Social Alerter crosses the line into popularity and starts becoming a strain, I'll have a re-think as to how to fund it. Whatever happens, SA is here to stay!