There has to be a very compelling reason to switch. Laconi.ca/Identi.ca might end up being somewhat successful, assuming it can survive it's growth. The win there is that businesses can start their own federated Laconi.ca instance to talk to other Laconi.cas out there.

But, there's still the problem of Twitter. There are so many Twitter based apps out there, that spread their brand which means there's about 6 gazillion sites other than blogs, and now news sources like CNN, that actually promote the use of Twitter. Twitter is big.