I personally do not get it. There are two threads, one thread at WebmasterWorld and an other at SEO Chat where people are literally arguing over the concept of hyphenated URLs being penalized by Google.
The threads were all started by members who have had sites suddenly drop off the results. The only thing they noticed was that their particular sites have 'over used' the hyphens in the URLs. However, many others are reporting that they 'over use' hyphens in the URLs and they have no problems ranking well in Google. In fact, they believe that is actually helps their rankings.
I am torn in between, I have seen posts at other forums discussing this as well, this seems to be happening more and more often. I am thinking that maybe a flag is raised on certain sites and then a manual review is made. However, we all know how Google hates to do anything manual. I really do not know what is going on here but I think it is important to mention.