[unityByFreedom]

If captchas are a bug, try running your own popular web service, and good luck keeping away the spam.

An extension is easy to install and is a reasonable way for the CDN to verify that you're not a spammer without requiring you to repeatedly prove it whenever your IP changes.

[cnst]

Your comment would make perfect if this whole captcha thing was required in order to post comments.

But they require it for static-like content that any decent site should be serving from cache.