Wide open wikis always have vandalism to worry about, and each contributor will have divergent writing style. A closed wiki can keep the content concise and format consistent, although it puts more workload on the mods and ambassadors. Ultimately, wikipost is still better than morsels of information scattered throughout the thread.

Prepaid mobile in USA is relatively simple with the few number of carriers and MVNOs. I think it will be fine to exist as a section in a wikipost with world-wide focus.