People like being paranoid when there's little reason. Even the end of this article was a slightly paranoid. I don't thing Gmail is shutting down anytime soon, it will probably last longer than any random domain a person buys.
The point is that you're locked into a single provider and it's hard to switch. Using your own domain isn't much harder, looks more professional, and allows you to switch provider at any point in time.
I love the shit out of Gmail, but I switched to Apps with my own domain for this reason. I've had my email address for much longer than Gmail's been around.
