As a brazillian, yes, there are lots of points in common. Also, orkut is pretty much dead now among my social circle; facebook has pretty much got all users of orkut and some more people who wouldn't have joined orkut (like parents and grandparents of the orkut generation).

As far as I know when orkut came around here there was simply no other social network with a significant number of brazillian members. Myspace was just too complex to understand, I think, and part of the annoying things of early orkut's design (you had no news, so had to keep checking your friends' and comunities' pages out to see what was going on, which fostered a whole cyber-stalking culture of checking people out) really clicked with a lot of the demographics.

I think more than by analogy that the dating market over here is also underdeveloped, and there is definitely demand for something that caters more closely to the brazillian forms of dating (which are different from the european forms of dating, and from the indian).