i'd rather a platform were i have to be careful to avoid malware rather than a platform were there is a single 'gateway' to what apps can be installed. how can that gateway ever be considered impartial in a for profit system?
If that's what you prefer, it's your choice: don't use OS X Mountain Lion (or use it, with Gatekeeper turned off). You (and I) can understand FlashBlock.app is a malware and wouldn't install it, but ordinary computer users don't, and that's the market Apple is after.
i'm not saying your wrong. and i definitely agree this is aimed at average users. but it will put off a percentage of non average users. and those are often the users who recommend to average users what to use. i know i've stopped recommending apple hardware after a decade of doing so.
whether this affects apple negatively overall is the big question.
I once got a virus on Windows that was attached to an Installshield installer for a legitimate program (WarFTP) that had been posted to download.com.
How could I have avoided that? Something like GateKeeper would have been nice - at least I would have known that the installer had been meddled with. Otherwise?