Way, WAY too much sandy vagina in this thread.
I was at the Blizzcon panel when this was announced and believe me, there was no booing or bitching at this decision. They clearly have some major plans for the Starcraft franchise.

Guys, take a breath and consider: Instead of waiting at least another year for the game, you get the Terran SP campaign and the complete MP(which has been done for a while, now) in the box. And, seriously guys, did anyone think that Blizz wouldn't release at least one expansion for the game?

Lots of you could care less about the campaign and will fire up Battle.net right away. You get all the Terran/Zerg/Protoss multi-player goodness right away.
Any updates to MP will be deployed through B-net the same way it is now, so no one is left out.

When the other campaigns come out, they will undoubtedly have some cool new additions as the game matures and the devs see how people are playing it. Probably some new units we haven't even seen yet, plus improvements to the editor for modders.

If the game has the same legs as the original, you will be playing it years from now, as well, so how do you not get your money's worth?

Yes, Battle.Net's future is still unannounced, but Blizz knows they have a good thing going now. Do you really think they would screw that up with a subscription or pay-to-play model? Just wait and let them announce the actual plan before you all jump off the cliff.

Think back on Blizzard's track record: Do their games just suck? Do they still support all their old titles? Do they at least try to keep the cheating to a minimum?
I'll go with a proven track record and keep an open mind.