I hate the term "securing the network".

Mining prevents double spends, that's all it does.

It doesn't prevent your bitcoins being stolen or make you whole afterwards, it's not analogous to a security guard standing outside a vault, or the government guaranteeing your deposits.

I'm mildly optimistic about about crypto currencies in the long term (10 years or more), but energy usage is the weak point of bitcoin, I wrote about this here http://www.reddit.com/r/Bitcoin/comments/195k4o/the_case_for...