i haven't done it myself, but obviously there are people who do it
i'm from Central EU and there was an invite only social network mostly for Hungarians called "iwiw", basically everybody who had internet in my country was on it (a few million people - "On Dec 24, 2008 the number of registered users on iWiW 4 million, covering almost all internet users in Hungary."), i say "was", because it was discontinued 2 months ago, it was much alike facebook, so FB killed it slowly, although it was started 2 years before facebook, and my point with this is: my inbox was always flooded with spam, especially lately, so it was used for marketing purposes despite in my country internet marketing is still not a well or widely known thing in 2014
you can imagine what kind of "damage" can be made on a network like this where you can reach basically a whole nation
if you're a coder yourself or you can find somebody who can make a bot and you have the right offer or even a local service to promote, you can have great results, competition won't be that hard and the security measures more than likely won't be that strict
however i can imagine the Russian social networks are already spammed to death, maybe no
but there are always other countries to look into