Starting a forum, social network etc is extremely hard. You have to reach a saturation level at a very rapid rate for it to succeed. Less than 1% that try actually survive.
You have to have a large community of users that all have a need for a narrow focused social network. Think hobbies, lifestyle etc...
If you have a blog with a huge following or a very large targeted email list that you are already communicating with, you could have a chance at creating a social network. Otherwise you would just be wasting your time.
Look at how big a flop Google+ was.
They spent millions of dollars and failed miserably.
Now if you want to just have one for the fun of running a ghost town.... Now that's a different story.
But, the software seems nice.