Right now webmentions are very much a DIY thing. Lots of coding involved, very ick for most people.
My thought is that, if Webmentions can head off the same abuse issues that plagued Trackbacks it's very conceivable that we'll start to see support for them baked right in to WordPress and Squarespace, and then it's off to the races.
But supposing webmentions don't work out at all, there's a (potentially much simpler) fallback: your RSS reader simply watches for links to your site in the feeds you've subscribed to. In Twitter parlance this means you only see mentions from people you follow.
UPDATE: With the proposed Vouch extension, you could receive mentions from people you follow and anyone they follow.