RenderWeb is now supporting PNG outputs for any Alpha Channeling the community may want to do.
There was a glitch that caused RenderWeb to be down for about 10 hours last night. Facebook updated some of their communication protocols, and as is with the Facebook Developer world, there was no communication about this.
However, today they have updated their server side to better communicate with Facebook. Everything is up and running smoothly.
Also, with the fun release of 2.57, they have also updated their renderers to operate with this latest version. So on top of the PNG, JPG, & High Res video Output Formats; the 100MB file uploads; heightened security; they are also now socially rendering Blender 2.57.
Fun stuff to be sure and it looks like RenderWeb closely follows what the community wants and needs. Now that is service.