The whole property & casulty industry has been hit hard. Many will lose money this year due to Japan. BRK's re-insurance is no exception. They will have to jack up premium for the next few years to recoup their loss this year. The key is, as long as the business is run properly, insurance makes money.
Most of BRK's subsidiaries are well-run business. They produce real things. There are a few bummers, but they're much smaller in size to the rest of BRK.
The thing I dislike about BRK is, it has never issued dividend. It's hard for investors to wait long long time without seeing a dime. To me, this makes it less attractive than other insurance companies. It's also difficult to apply FA or TA on BRK.B, which makes the stock less tradable than other high swing stocks.
Disclosure: I have always owned BRK/B. I simply add/reduce my holdings over time.