As someone who often bills hourly, I'll go with $0. Your time isn't fungible; it only commands a bill rate if you can commit to a start time, milestones, and a delivery date. Very few businesses want to pay for your spare cycles.

I realize that I may have sparked this line of argument with my quip about the time I spend posting on HN. But the fact is that for every hour I lose here I might well save an hour somewhere else, because some person posts something about github, or Linode, or Dropbox, or some other tool that I might otherwise never have heard of and I get that much smarter.

Time spent socializing with smart people is very difficult to value in dollars, but it is certainly not valueless! If nothing else, it preserves one's sanity and morale. And these are very hard things to buy, indeed.

If lost billable time is spent on Hacker News, then how is paying $5/yr for a subscription going to change anything? Your clients will, apparently, still be losing money.