It launches by itself, I actually encountered this just an hour ago, I was surfing google images, and the application downloaded and launched it self, although of course I cancelled and deleted it..
But if you disabled "Open Safe Files" on Safari then it doesn't launch automatically..
Anyway it's not really a problem for computer savvy people, but I think my parents would easily install this without knowing that it's actually malware..
So It's still an issue I think, obviously this is something that Windows has had in the past, still It should be no surprise, as more people begin to use Mac OS, viruses, trojan, malware/spyware will be a part of Mac OS, it'll be interesting to see how Apple handles this problem..