Just thinking out loud here.
So we all know that they shared the computer and someone wiped the browser data.
For someone that also uses his computer, Josh going to a party should be the perfect timing for someone to watch porn on his computer. Just think about it. Maybe someone was using his computer for that purpose and Josh going to the party was the perfect timing. So when you find out he was missing you must be scared that the police is going to see your history so you will probably going to delete it. Just something to think about. Since the computer is shared we can't know who did something, do we?. Also I do think the report that Josh made to Yahoo is important, maybe Yahoo can help...
I just want to say that I hope this case will be solved and especially all the love to his family and friends who are still wondering what happened to their son/friend to this day. Keep on writing about it. And also for people that know information, don't hesitate. You will not be judged by Josh or anyone here. It could help you relief something and I also hope the best for you.
I think it's important for anybody, even outside america, to let know their findings or opinions. Because when I was reading some of the posts here, I was jumping to conclusions that weren't in the posts. Your brain will try to figure it out while you read.