There are almost *1000* one-and two-star reviews on Apple's own store detailing how the Magsafes break, over and over again, in exactly the same way, in exactly the same place. Unfortunately, a few people keep trying to pin the blame on users for not handling the adapters properly. It's beyond obvious that they're defective, faulty, dangerous products. Which is precisely why they changed the design for the MBA. I imagine that design will start showing up on the MB and MBP before long.
I've been fortunate enough not to have problems with my Magsafe adapters but I know plenty of people who have, and it does seem ironic that something with "safe" in the name is clearly so dangerous under certain conditions!
The Magsafe on my Air is a far better design than the original ones, and hopefully Apple will migrate the Air style tip to the rest of the range