If you’re running a blog or personal website, be sure to IndieWeb-ify it for maximum site-to-site engagement. Use micro.blog or the various IndieWeb plugins (or find lots of other options on http://indieweb.org).
I see a potential for spam, but on the other side I always found that given the low number of webmention-using blogs, they do not seem to bring a lot. Most posts where Ibsaw them used were posts about webmentions themselves, where people basically were playing around.
Such an aggregator would at least create some kind of hub where such posts appear.