RIU would have to hand over the IP logs that they keep. Its all up to how trustworthy RIU is. I am fairly sure they are located in the US, so if a court orders them to hand over IP records, they pretty much have to. A court wouldn't do that unless they had a specific person they were going after. Basically, I will never post any pictures on here, or talk about anything I am or am not doing. I don't incriminate myself at all. A lot of people do, but that is up to them to take that risk.
BTW, it does not take any resources at all. It takes a subpoena and a letter to RIU. Then RIU either chooses to comply or faces legal action.