Well Twitter made about $665 million last year, with much larger projections for this year. I would say that qualifies as "decent".

Twitter lost $645 million in 2013. I'm not sure "spend $2 to make $1" necessarily qualifies as "decent".

They didn't lose $645 million in spending, it was a one time recognition of the stock they already allocated.

They've still yet to make a profit.

It's decent to all the other companies out there that are now valued in the billions of dollars for reasons unbeknownst to me.

Has SoundCloud come up with a decent monetisation strategy yet?

It's freemium, but the premium accounts are actually worth buying. You get more upload time, better stats, more customisable embedded players, etc. Lots of people buy them, I assume it's already quite profitable. The "prosumer" market for music production is expanding enormously at the moment with the american EDM boom.

If twitter shuts it down or ruins it, there will be blood. A lot of people depend on it and there would be instant demand for a replacement if the userbase turns its nose up at any changes.

OTOH anyone promoting their music on SC is almost certainly already doing so on twitter as well, so some simple, well executed integration could go a long way.

bandcamp could integrate a social community aspect? they already host music?

Bandcamp already let's you follow other users and musicians and view the albums they've bought/want to buy.