Say I'm at a coffee shop with wi-fi or using my notebook through a cellular 3G/EDGE network and this update starts downloading a large Google Earth update that I never asked for. Why should I be paying for the charges because Google wants to update their software without telling me?
Another issue is versioning. If I'm working in one version of the software and don't want to use the newer version until others thoroughly test it and fix the critical bugs, why should i be forced to upgrade? I've used a lot of newer versions of software and many were actually worse than their older versions. Again, why should they force users to upgrade? Why not ask?
This Google Update is bad news all around. It installed itself like a virus rootkit on my machine with Google Earth installation and I was never notified (yeah, a note is probably buried deep in a TOC somewhere). Luckily, LittleSnitch told me about it and I removed it from the Launch Daemons... and I also removed Google Earth because of it.
Finally, why should Google get updates about my location at all times? Every time this thing pings their server, my IP is inevitably transmitted to them.
Sparkle does this perfectly. You can completely disable update checking or allow it to check on periodic intervals. And when it finds an update, it informs you with an update window and shows you exactly why it is updating and what was fixed and what more you get. This Ohama thing gives you none of these options and it also runs at all times like a virus.
If MS did this, people would be all over MS. But when Google does it, people defend them.
Any software that adopts this Omaha crap will be blocked from my machine as well.