Write Only Properties?

I was recently going through a colleagues code and noticed that in several places he had added write only properties. i.e. Set without a Get

In this case, he just happened to be a little on the lazy side, but it got me wondering, how often do people actually need to use write only properties. What are the reasons for having them?

The only possible thing I can think of would be security (all be it very limited), but surely there would be very few places where this sort of functionality is required.

I'm interested to hear other peoples feedback on this.