do you "eject" USB flash drives before you unplug them?

[space-time]

I always eject (unmount) the volume, both in OS X and also in Windows XP. However, I noticed that the majority of my colleagues just unplug the drive.

When we work together at my PC and they reach for the drive, I say "Hold on a sec, let me eject this" and they give me the deer in the headlights look.

So, is the "eject" or "unmount" necessary or not?

of course, we assume there is no read/write operation going on at the moment.