- If necessary, work on ways to cut spam to manageable levels, like simple CAPTCHAs.
What about but "questions" are not ("Result for 3+5" + textbox, "What's your favourite scripting language?" + textbox) instead of captchas?
Also (althought it breaks mobile access) html5-game-based captchas (see
http://areyouahuman.com) seems to be a nice idea.