Which default selections do you find there to be an issue with?
For
example, some office suites items shouldn't be cleaned in some situations. For some users (depending on how and what they installed from the complete office suite), cleaning the office item will not have unwanted consequences. But I indeed have seen cases where cleaning office items in CCleaner has been a very bad choice (no matter how much free space you are supposed to gain).
In fact, cleaning Avast with CCleaner by default is also a bad choice. Only when the user has some specific goal, and he knows what he wants to achieve, the item ("Avast *") should be active (checked).
Some registry cleanings are also not "so much recommended".
So, what I'm trying to say is that CCleaner is good and welcome, but IMO the "factory defaults" are not always "safe" as other users are saying. That's why I don't recommend it with a *general* purpose, but only if I give specific instructions on which items to clean (and all the others UNchecked).
This is my own experience and opinion, and other users are free to have their own.