OK, so my example was a bit contrived.  In most cases what we do in our critical sections would be more than just adding to a List<>.  And in those cases, if an exception is thrown, we would hold the lock.   The next thought that came from that was that if you use an established pattern (lock), then why mix?   I believe that you should use the right tool for the right job.   I will have to chew on this more before I acquiesce on this point, however.   I would like to hear other opinions.