I could see a few use cases for Android on RPi; faux tablets, car PCs, HTPCs, etc. Personally, I was going to experiment with it as an HTPC, since it'd probably be the best possible option for Netflix streaming (at least, unless and until Netflix finally releases a Linux client). What I'm saying is that, while there are better options for general purpose computing, Android is compelling enough to be an option. I might just experiment with compiling it myself if nobody else is willing to do so.
As for what was said earlier about Android being somehow "fake open", I'm not sure what the issue is. The source is readily available, and is used in a variety of other open projects, from CyanogenMod to Android-x86. Heck, their changes are even getting merged back into the Linux kernel. Google's apps are closed, true, and Google made it to make money, true, but frankly, Google has been very good at giving back to the community that it has built its products on. And no, ad blockers don't get removed from the Android market; I've had AdFree Android on my phone since I got it, with no issues.