Yeah, in the circles I run in it's usually used either to refer to a fictional character being endearingly silly/dorky or to refer to oneself having an airhead moment. I haven't ever seen it used to mock people with disabilities, but my internet presence is really fairly limited (which is to say, I spend a lot of time online, but mostly on about four different sites).

That being said, I've never used it much myself and will be careful not to do so in the future now that I know people are uncomfortable with it. ("Adorkable" is a more fun word anyway.)