I always find it interesting how paranoid people are about this, coming from a country (Norway) where you not only generally have the right to 3 months notice, but also have the right to continue working during your notice period (a result of seeing work as a right and requiring very compelling reasons to take your work away). There are exceptions, such as e.g. if you're fired for cause, but they are quite limited.

In reality, it causes few problems - people likely to do something malicious probably already did it behind your back anyway.