I totally get why they do it. It probably works very well to deter outside influence as well as unwise tweets. But I would have a huge problem with it if I were a PNM. I'm capable of following rules like "Don't tweet your prefs!" without having my hands tied.
Does a PNM get her phone back when SHE is done ranking, or does she have to wait until the 2250th Unsure Uma makes up her mind?