I guess there'll be cases of a Steam title or somesuch that's too risque for iOS or Play but which could be ported to PSM. Good luck to Sony if they hope to grow their PSM business to a mainstream moneymaker on artistic merit though. How many art-house cinema's are booming cash-cows thanks to their artistic integrity?
I assume Sony would point to something like Journey being one of their most successful PSN titles.
Anyway, obviously it's just one approach they're taking to indy developers, and risky here also just means that it's a low-cost investment. This can also be for a massage game such as is found on the Japanese store, that has little artistic pretention, and is risky in a more down to earth manner.