Large angels in a reef. Your thoughts?

[Delphinus]

I'm always surprised to see how many people have larger angels in their reefs. I always had the thought that they were risky in a reef due to munching on things we'd otherwise pay good money to keep? SPS, clams .. LPS. ? Is that true or is it more of a case where they eat sponges, and whatever you feed them, and they leave the rest alone?

So.. I'm curious. If you have an angel (or angels) in your reef (excluding the Centropyge sp. pygmies that is), is there anything you've found that you can't keep in your reef as a result of having the angel(s)?