However, when there are really hard trophies related to Multiplayer, like reach max rank or unlock a top tier item, I really begin to dislike it. The only exception to this is by making them unlocked with DLC. Since people buying DLC are going to be dedicated, I think they can handle the tougher Multiplayer trophies that may come with them (most of the time, since Uncharted 2 had that nearly impossible "You Run, I'll Shoot" trophy ).
So, in the end, I prefer to only have Single Player trophies, but I'm fine if the MP trophies are simple to obtain. I prefer that developers save any tougher MP trophies for DLC packs that they may release.
Some games do online trophies well like Mass Effect, allowing you to do it online one way or offline another. However online trophies as far as im concerned should be banned. You should never make a trophy that in the future people will not be able to get because you shut down servers it is just ignorant and lazy. It will never happen and it doesn't matter but they are still terrible, I have all the single player trophies in many games but due to multiplayer I will never get the platinums.