[bluedevmonkey]

There are some alternatives, i.e. where Captchas are only displayed when JavaScript is disabled. But all these methods don't work, at least someone just can analyze the traffic and do all the JavaScript-Stuff in a single HTTP/TLS Request, because it's not truly server-side. I know it's embarrassing to use Captchas, but at least for the registration it should be used. Or you could use OpenID or some social network oauth system to avoid Captchas.