I locked my BD outside a pub last night after hauling the GF there across town [she hurt her knee so no biking for a week]. I use two thick cables one around each wheel and then use a kryptonite chain with padlock to secure the main frame and cables to the metal post of the bike rack. I pulled my lights, but leave my Brooks B17, Porcelain Rocket bags and the Xtracycle stuff at the back unlocked.

I've never had a problem and my biggest worry isn't theft - it's vandalism since the BD is an odd ball it tends to attract lots of attention.