Firmware updates, use discretion..

A lot of people? I've only seen a few reports of this happening.

What brands/models has this happened on?

And don't some TVs update themselves automatically?

Samsung yes, Panasonic no for the most part.

Samsung occasionally issues a firmware update to fix an issue, but they also include widget updates. When you go to use the certain widgets you will be stopped and told to update first.

I have a samsung pn64d8000 plasma tv and samsung sent out a new firware update. I downloaded it and went thru the process and after the new firmware tv would turn on and off all by itself with no reason. Called samsung told them what happened and told me it would have to be sent in for service. I told them that it worked perfect before thier update and they didn't confirm it was anything to do with thier update. I was so mad that i cursed them out and i paid at that time $2500.00 for this set. I sent it in and they said it was one of the main boards. Had it fixed in one day. Amazing Samsung had this board in stock. Anyway they were very kind and paid for it all even thou it was out of warranty. All said and done i will not be updatting firmware any more.