What is the name of this throw?

It has several different names depending on he culture or style of fighting or sport.

In judo it is ura nage (rear throw)

http://judoinfo.com/images/animations/blue/uranage...

suplex

http://youtu.be/b8E0RoFmHS0

There are some other names too.

Yes it is effective if used in self defense! The ground is less forgiving than the mat. It is a harder surface than your fist. You can easily injure the attacker neck, spine and or head.

Yeah, it's pretty much just a straight suplex. Kind of looks like a judo ura nage too. Slamming somebody in a street fight is rarely a good idea. The legal liabilities would be absolutely brutal, but there's no reason it wouldn't work in a strictly physical sense.

Suplex throw

Probably suplex.