I picked no...not so much because Dean forbid him. He didn't really forbid it. It was more like he begged Sam to see the bigger picture and at the time, Sam just wasn't able to. It would have been better for both of them had Sam steered clear of Ruby. But that just wasn't his destiny. ;)

I didn't like Sam working with Ruby. She used him!

yes its true,ruby was using him for raising Lucifer,me and dean were very disappointed at the finale of SEASON 4.:(

It's complicated! I think it's both because she was just using him after all! but even so she actually taught him things and she did fight on his side until the end!

That is such a complicated and debatable question, but he thought that she loved him. So, he didn't realize that the demon blood was addictive until it was too late when his mind was all messed up and he wasn't thinking straight. Of course; it is a little weird to drink someone's blood, but everything in SPN is weird so thats normal for them. Plus, he felt so bad after that! He felt like he had failed Dean and the entire world so it is not like he was trying to mess anything up and raise Lucifer. Also, ever since that happened; he has been like trying hard to not mess up which was proven in season 8 when he didn't want to stop the trials because he didn't want to fail Dean and the world again. So, yeah, gr8 question! :)