Take a look to this site: Loggly.
Great idea and very useful. I've been thinking about this for a while, and today a college brought up this startup to the conversation while talking precisely about doing something like this for our own applications.
Can't wait to try it and see how it goes.
Anyway, I think every developer with a real application out there should think about using something like Loggly. Or maybe create his own personal version. Keeping logs of our apps is really really important.