I'll take a shot...
Part 1 - Fanboyism could be the cause of an emotional bond to something. For example, if somebody grew up around Mustangs their whole lives and they later find out that their dad's first car was a Mustang, maybe the person links Mustang's to their father. That bond is greater than any numbers or proof about something than anything else.
Part 2 - I'm thinking that they want to be part of the crowd, to be accepted by the crowd that is. Or, they might just want the rest of the posters/readers to see that they also agree with the general consensus. Would it be okay, or the same, if the poster only posted "+1"? Or does that still count as redundant?
