The original Orkut site was written in C# - it was very slow and couldn't handle the growth. Orkut was only a big success in countries like Brazil and India where internet connections were already so poor that nobody noticed how slow the site was.
And facebook was written in frikkin PHP. That means it was not C# that made it slow, probably just bad programming.
> The original Orkut site was written in C# - it was very slow and couldn't handle the growth.
These are orthogonal facts presented as if they were related.