Don’t.
If you already do, move someplace else.
Why?
Welp, if you ask me, one of three things will happen:
1. Twitter will wait a few months and then shut Posterous down permanently. I feel this is *far* and way the more likely scenario.
2. Twitter will subsume Posterous’s talent and effectively ignore Posterous the service (while letting it run to avoid user backlash). It will turn into this year’s Friendfeed: a great service, acquired then abandoned. It might stay up for awhile, possibly years, but there’s (effectively) nobody watching it.
3. Twitter will devote both resources and people to the Posterous service and apps and it will blossom into the delightful young starlet we all hoped it would be. I’ll be shocked if this happens, but it’s technically possible.
With all of the other options out there, I think staying with Posterous for longer than the next month would be the wrong decision.
Learn from history, folks, because it’s about to repeat itself here.