Clean your Mac
Tremendous amounts of „Clean your Mac" is on Web; are it known and observed securizy attacks?
As I understand it, MacKeeper is "ransomware". To get the uninstaller, you need to have purchased the software, so the "free trial" is a nasty marketing ploy. Whether it is any good is a matter of opinion, there are some terrible user comments on their website.
I use OnyX for the occasional big cleanup and resetting of caches. But with the coming of 10.7.2 and iCloud, even with this, I am waiting for a compatibility update before I use it again.
I hope, one day SpyBot S&D and Ccleaner will become Mac friendly...