I haven't updated this for a while, but...
As of 2013-07-26, the hour balance is -142.9 hours.
As of 2013-01-29, the hour balance is -102.1 hours.
Obviously we've been putting a lot more in the last three months than we're yet getting out.
As of 2012-10-28, the hour balance is -48.5 hours.
As of 2012-10-12, the hour balance is -44.6 hours.
As of 2012-09-16, the hour balance is -41.5 hours.
So once every so often, I'll publish an hour balance. If negative, we've spent more time on the site than it's earned. If positive, it's made more money than it's cost.
I thought it would be an interesting experiment with ThoughtStreams to be transparent about how much work has been put into the site versus how much revenue it's generated.