I'm assuming this is a bug; it's certainly odd.
When I open the OmniWeb Plugin preference, it lists pretty much every plugin on the computer (including plugins that aren't web plugins) as loaded. Apparently OmniWeb is loading Saft (Safari-only), Inquisitor (Safari-only), Chax (iChat), CTM Assistant (chat logs--
link), among other, normal web plugins.
I've disable everything that wasn't a web plugin, but figured I should point this out (have also emailed to support).