I've been approached by vendors on the floor of many trade shows - not while at their booth but while looking at another product. It's a good way to find people who might be interested in your stuff. And I've also been invited to attend off-site events while on the floor of a convention.
I agree that a lot of vendors also take advantage of their customers and potential customers all being in the same place at the same time, to convene them at after-hours parties and events, with invitations issued ahead of time.
CES doesn't have the moral right to kick you out of your hotel room - but it appears that they have sufficient influence to do so. I'm not saying it was right - but it appears they did it, and unless big media picks the story up, they'll probably get away with it.