How Much is Too Much? Where is the Value in Attending Conferences?

After exploring for a while the  Consumed to Thrifty thread, I thought it could be useful to see how this applies to picking which conferences and events are worth attending, what their value proposition is.

Have you felt at times like your time and money would have been better used taking a vacation instead?

Therefore I offered a session looking at this topic during the Open Conference part of Web 2.0 Expo New York (September 16-19)...