I'll bite with a good f.b. lockup story. I had just gotten my conversion with a flip/flop hub and was riding the freewheel to get used to the bike. I was coming up Mass Ave in Cambridge from MIT towards Central, which meges with main street and I blew a red light. This is typically fine because you have a good view of the folks merging from Main and I could clearly see that the only thing that would get in the way was a moped that would (I figured) merge well ahead of me. I was probably going 20.
Anyway, the person on the moped noticed me right as she was meging into traffic and--I have no idea why--got scared at my approach and stopped dead in my path. I looked at her, she looked at me and I suddenly realized she wasn't going to move. Slammed on the front brake and next thing I knew, I was flying over the handle bars. After getting up I did the following things, in this order:
1. Ensure that I hadn't scratched the bike. I hadn't.
2. Check to see that she had a red light and that's why she stopped. Realized she had no light at all.
3. Yelled at the top of my lungs, "What the **** were you doing? Why on earth did you stop?"
4. Realized that she was a very nice, very bewildered, very attractive Italian woman on a celeste-green Vespa.
5. Apologized profusely, took all blame (well, it was totally my fault), and left saying, "Oh yeah, everything's fine, I mean I didn't even scratch it."
6. Bought a bike helmet.
Not sure this would have happened if I'd been riding fixed.