At the very moment my bike has 2 Kryptonite New York Fahgettaboudit Mini locks, Kryptonite Evolution 4 with a Kryptonite cable. For added security I have a Pitlock skewers and have my Brooks saddle chained to the frame. This is my locking system at home. Is it overkill, most likely but bikes are stolen from my condo building enough to take this extreme measure. My wife's bike right beside it has the same set up.

When I worked in downtown Toronto, I used the same set up but I left my locks attached to the bike rack so I wouldn't have to carry them home. Currently I have 10 Kryptonite locks, 3 Kryptonite cables, and Pitlocks for both bikes.

After having a few bikes stolen with 1 Kryptonite lock I up the ante and haven't had a problem yet. Would I spend $200 on locks for a $500 bike? The answer is yes. They are used more as a deterrent. Your bike needs to be more difficult to steal then the bike beside it. Plus the locks are long term investments, they will outlive your bike and you can use them on the next one.

Some cities have higher rates of bike theft than others and you have to weigh the risks.