Yeah, but those are the only (or at least the primary) kind of companies that would seem to fit a reasonable definition of "Bitcoin business."  If you deliberately set out to start a "Bitcoin business," it will probably have something to do with exchanges or moving money. If it doesn't, you're almost certainly setting yourself up for failure.  

"Bitcoin is so cool! I want to start a Bitcoin business! Hmm... I know, I'll make custom hats with my Bedazzler(TM) and sell them online for bitcoins!"

Well ok, great, but you're forgetting something.  Bitcoin is a currency and a payment system. It's not a business plan. It doesn't magically make the goods and services you intend to provide valuable. Now it's true that in SOME cases, the revolutionary properties of Bitcoin might enable a completely new business model (e.g., Silk Road), but that will be the exception.  For the most part, what you'll see are existing businesses adding Bitcoin as an additional payment option.  Making it the exclusive payment option is (in almost all cases) like opening a fireworks store that only sells snakes and sparklers -- it probably won't do great things for your sales numbers.  And things will likely stay that way for quite some time as Bitcoin becomes more widely known and used.  But remember - the fact that a hat seller allows you to buy their hats using bitcoins doesn't make them a "Bitcoin business" any more than their acceptance of dollars makes them a "dollar business."  So if you want to start a business that leverages one or more of Bitcoin's unique properties (e.g., ability to send micro-payments), then that's great.  And if you just want to sell Bedazzled hats, that's great too.  But in either case, understand what you're getting into.