I agree with that.
I agree with maxorator - in the apps we've made at work we use that feature - and it rounds out the functionality of a webapp quite well. I don't think it's inherently unsafe at all - if people are worried about it, they should by all means block it as mentioned above, but it really can't do any harm to your system. You just shouldn't visit sites if you know they're dumb - that's the only site I've heard of doing that.
Lots of websites do things without your permission - if you were to disable all of them, you wouldn't have a very useful internet experience.