[Godhelm]

... and how can I stop them?
... or does it not really matter?

[allotmentann]

Probably slugs, they like beans when they are young and tender. If they eat all the leaf off, they are unlikely to recover. If most of the leaf is left even though it looks unpleasant, they usually pull through. I lost several sowings to slugs last year.

[compostqueen]

"What's eating my beans?"

The dog!  He snaffled my seed order as it came through the letterbox this morning.  All my beans seeds covered in drool and holes