I'm wondering if using autocomplete fields, like SO uses for tags in question posts, goes some way to filtering out spammers/bots.
If the field requires a user to make a selection according to some simple rules, this may mean that the bot can't proceed effectively.
Any thoughts?
Autocomplete has no effect whatsoever on spam bots. It does not affect anything they do - it's only offering suggestions as you type. You can type whatever you want, totally ignoring the suggested text. Spambots likely won't have the Javascript enabled that permits autocomplete to work, anyway.