I believe you are correct about this UK Bob

I remember people complaining about CCleaner deleting the prefetch folder by default up until about 8 months ago until they were convinced that there was no need to. It's still an option though. But asyn is right about it containing little bits of information (that most people couldn't care less about others seeing) like location where programs and files are saved on the computer and if I'm not mistaken the last time they were opened.

You should delete it once in a while though since it fills up more and more slowly defeating the purpose of it (especially if you move files around a lot or install/uninstall programs often). If you keep it the same to long it will in some cases slow the computer more than speed it up.

I usually do this monthly or by-monthly