Are rails worth the risk?

Ok guys, my friend and I have been wanting to build some rails for this summer. However, we are debating if it is worth the risk of losing your board. I hear about a lot of people breaking their board when they do rails, and even if you have a warranty, nobody will fix or replace your board if there is any evidence of you using a rail. Can any of you who have ridden rails answer me 2 things...
1)What is the chance of breaking your board?
2)Is it worth the chance?

Thanks