These are some crude measurements, but I looked at all threads with a "last reply" from Jan 16th, 2011 back to Jan 18th, 2010.

Number of threads = 3247
Number of threads with no reply = 657 (20.2%)
Number of threads with one reply = 968 (29.8%)
Combination of no replies or one reply = 1625 (50.0%)
Total number of views = 2,481,963 (average of 764 views per thread)

Thread with the most views = 27756 views -- RTC versus Jira/SVN/CruiseControl by maryxebere
Longest thread = 32 replies -- Good practices for setting up RTC environment by sims

I included "one reply" threads in the measurement because it means somebody made an effort to answer a question but the original poster either never responded back or never realized their question was answered. I'm willing to bet that over half of the "one reply" threads are cases where the original poster forgot/didn't know to check the box "Notify me when a reply is posted" and therefore assumed nobody answered their question. Is there any way we can make sure this is fixed? It might lead to a 30% improvement in forum quality :)