Why does it need to? Is it self sustaining? Maybe that's all it needs to be.
When you try hard to commercialize and squeeze profits, things change and you lose audience. This is exactly what it is limiting the lifespan of Facebook.
"This is exactly what it is limiting the lifespan of Facebook"
Facebook has over a billion users and has been around for ten years. No other social network can claim both of those things. Don't know if it qualifies as an example of a "limited lifespan"
I think he isn't saying it has had a limited life span. He is saying that it's future lifespan is being limited. Basically, he thinks it has potential to go on much longer than it will.
When you try hard to commercialize and squeeze profits, things change and you lose audience. This is exactly what it is limiting the lifespan of Facebook.