Every modal dialog plugin I’ve seen takes the following approach: try to anticipate the ways people will use it and provide configuration options accordingly. The problem is that as soon as you require anything the developer didn’t anticipate, the plugin becomes useless (or you start messing with the source). If you’ve read Spolsky’s essay, you’ll recognize this as a leaky abstraction.

Veneer tries to minimize leakiness by doing the absolute minimum while making it simple to add anything you need (as in my third example).