True, though you can't click on what people are currently doing either...or copy it (I mean kind of, but not really).
I do agree that eventually email address harvesters could eventually be made to read them though, and that would be a big weak point if they ever did catch on.
- You can't copy them
- You can't type them
- You can't embed them in text
(Though, the latter two problems apply to some of the methods discussed here as well)
If they did catch on widely, it would be trivial for email address harvesters to read them (see: increasingly-complex captchas)