Most court proceedings are pretty boring. The exception being PPO hearings. If you are curious about the process, spend half a day watching them. Some of them are straight out of the Jerry Springer show.
Yes, you can challenge them, but your success can sometimes be up to the whim of the judge. I have seen PPO's with little or no evidence be upheld just because the judge thought it was better to be safe than sorry. I have also seen ones thrown out that should never have been thrown out. The other problem is that you only have a short amount of time (14 days) to file a motion to have it set aside. Another problem is that once you have one and the other party applies for another one when it expires, the subsequent ones are way more likely to be upheld.
IMO, they aren't revoked routinely. Considering their effects, they are upheld way more often than they should. If you ever get one, take it very seriously and hire a skilled attorney to aggressively fight it.