Going from PvE to PvP, and vice versa.
It occured to me after writing a long and involved bunch of paragraphs about why its not a great idea to do such a thing... i could just ask a simple yet probably-likely-to-bring-out-the-obnoxious-and-stupidly-ignorant-comments type of question.
and this is it:
If a game is built around a focus on a single of the two designs (PvE or PvP), do you SERIOUSLY think its just THAT easy to go "K, lets throw people into an arena and fight it out" or "Lets add some AI in, itll all be good" and keep the game as well designed as it was?
There. think about that before you ask every well designed PvP or PvE game to go both.
And Please, try to leave the prepubescence at the door will you?