is MacKeeper safe?

No — it's notorious malware. Do NOT allow it on your computer.

Never download anything from a popup, it may be a trojan masquerading as a useful application. In fact, it probably is a trojan. I feel sorry for the legitimate companies whose names and reputations are being besmirched.

There is an application called MacKeeper. If you want it, be sure to download it from their site directly not from a popup.

http://www.macworld.com/article/151454/2010/08/mackeeper.html

Okay, come on, now, let's not say things that aren't true. Is MacKeeper malware? No. Is it crappy software that does things that you don't need or could be done better by other software and that is sold by a notoriously unscrupulous and unethical company? Yes.

Minor difference? Perhaps. But it's better to be completely honest than to have someone learn that you weren't telling the strict truth and decide to discount your advice.

I think eww was referring to one of the aliases of MacDefender or whatever that malware called itself at the beginning. It went by other names as well. MacKeeper may have been one of them. The popup didn't claim there was a virus (or the OP didn't mention it) so it may not be that particular malware but I'd avoid downloading anything from a popup. Might be legit or might not be.

No, there was never a variant of MacDefender called MacKeeper.

Thomas A Reed wrote:

No, there was never a variant of MacDefender called MacKeeper.

Agree, however I did see reports that they used the MacKeeper 911 logo on the initial site where they tried to get you to download MacDefender. I think that may be where the confusion was.