My personal minimum for such sites is that they, as with other out of station areas of eve, act as a focus for competition, conflict and/or cooperation. If it is only one of these in isolation or even 2 out of 3, I do not feel that they add much to the tapestry of eve.
I can get behind dust battlefields as they encourage macro competition over planetary resources, immediate conflict and cooperation not only with your team mates but also orbital assets. If EVA game play doesn't allow for lower-powered but still tense and skills based acts of violence against other capsuleers, as well as cooperation in the face of that and possibly greater threats within the environment, then it isn't EVE imo.
Persistence is not required physically, but it is required in the minds of those who experience such game play - without the usual give and take in EVE and the chance to get caught with your pants down while looting some frozen starship tomb, what point is there to it other than 'need cash, do rote activity'?
TL;DR, It is my opinion that immediate cooperation and conflict require persistent competition (ownership of 'good places to go' be it spawn quality or quantity - or even market importance of rare, hard fought for goods) to meet the minimum requirements of being considered a 'toy in the sandbox'. Persistence of location is not required so long as, for the duration of an encounter, it is available to more than just those for find it first.