Why is “lock (typeof (MyType))” a problem?

Question

MSDN gives the following warning about the lock keyword in C#:

In general, avoid locking on a public type, or instances beyond yo

Answer 1

Because the result of typeof (MyType) (which is an object of type Type) is widely accessible and other thread can lock on the same object, and hold that lock indefinitely. Then internal logic of MyType has effectively given away significant control over it's synchronization logic. This might not be an actual problem if this is intended, but coding defensively/skeptically should be your modus operandi.