[sp00ls]

Every app I've installed that wants accessibility access follows the same steps from the comment you replied to. You must explicitly unlock that pane with your password after clicking the lock and then enable the app to have accessibility access.

[dunham]

It's also possible to detect input events from accessibility. Little Snitch detects and ignores those events (tested via "Synergy" - a keyboard/mouse sharing application), as does the download icon that appears in the upper right corner of iBooks (I don't know why).

The accessibility preferences panel appears to accept those synthetic events, however.