I have been using Google Talk for a short while now, and have updated it several times. I went into the directory it is saved in, and what do you know, any time you update it, it keeps the old installers in the Google Talk folder! See picture:
It would be nice if CCleaner had a feature to clean out these old installers, since most people probably wouldn't want to go back to a previous version anyway. They are just about as useless as Windows Hotfix uninstallers, and after a while, the space starts to add up, as you can see.
Off the top of my head, I can't think of any other apps that do this, but a feature to clean out old app installers would be useful, and could free up a decent amount of space.