@tkadlec @rachelandrew I've been using webmentions for a while and I really love it. It's transformed how I use the web. It also induces people to take greater ownership of the content they're posting to the web. (Tumblr did this in a sense as their form of reply caused one to post it to the top of their stream rather than hiding it in a separate tab like Twitter does). I find that with a higher level of ownership (actual) people are less likely to spam others.

If you want an example, I'm using Brid.gy to "force" Twitter to support webmentions, so you can like this post or reply to it on Twitter, and your comment (moderate-able) will show up below and my own site will send me a notification of your response.

Though there is a potential question of webmention "spam" (less likely than other prior methods due to the specification), some services like Automattic's Akismet are already supporting filtering for it.