We have at least two share buttons (often more with various add-ons) which are almost identical in physical size, appearance and functionality and then there's the Facebook one which is incredibly wide, includes which of your friends have clicked it and even includes photos.
Although this is clearly a nice feature, it does kind of look out of place compared to the others.
It's also tricky to make additional buttons look any good when they're so far away from all of the other buttons thanks to the Facebook button being 500px wide whereas most are about 100px.
For my most recent add on I had to do str_replace on part of the template hook just to get the button where I wanted it.
I think, all things considered, it would just be better to have the standard button.