I installed Lookout almost as soon as I got my phone, but I uninstalled it back last August for a couple of reasons. First was that there never seemed to be updates and I question any anti-virus that seems to not need to keep track of infections. The second was that I was getting weekly emails and while it said it did something, there was no way I could tell exactly what it did, if any. Also, I would first get the notice that an app was installed and then I got the notice that it was being scanned. Why not the scan before the install?
Maybe I'll look into it again, I dunno.