Google plus is the latest attempt to challenge Facebook’s social media juggernaut.  However, after initially strong growth, the service seems to be hitting a snag:
Sophomore Slump? One Month In, Google+ Sees A Traffic Minus

This underscores the difficulty in going up against a business with established traffic and users.  When even Google runs into trouble, you know it’s hard.  It’s why nobody has made a serious run at ebay in all these years.  Once users have established accounts with lots of data tied in, the switching costs are just too high to go to someone else.  It’s important to consider this when starting a business or website of your own.  Technology is not the obstacle – getting users IS, and that is the biggest challenge to overcome.