It's actually a common tactic to do this. Usually you'll see messages on the channels (I saw some on VH1) that the provider isn't going to carry them anymore, to call and complain.
The odd thing is, it's usually the provider that's in the right. For example, a couple years back Disney had to renew their contract with Time Warner. Disney wouldn't sign unless TW took on a bunch of other Disney-owned channels, and weren't open to compromise. So TW basically said, "Screw you, you'll negotiate or we'll drop your channels".
I don't know the number of Dish Network subscribers compared to TW, but it's essentially like playing chicken - the lost channels mean people leave the provider, but on the other hand it means less people watching the channels, and thus less revenue. I'm sure they'll be added back in time, though it sucks for all of you with Dish Network, no doubt.