Trackbacks have built the blogosphere. The automatic backlinking was a great idea. The both parties -- the original and the linking blogger -- were making benefit out of a trackback link.
Unfortunately, the trackbacks are extremely vulnerable to spamming. Indeed, trackbacks must work without human intervention (by design). Automatic filters doesn't work well for blogs. And adding manual force breaks the design of trackbacks.
Fortunately, there is a simple solution.
We have blog aggregators and blog search engines. These services know about each blog on the planet and they can
1) distinguish the spam blogs from the good blogs,
2) find all the blogs which links to my blog post.
Therefore, a tool can search for the new links to my blog and create trackbacks records in my blog.
Other variations are possible as the main idea is fruitful:
Trackbacks should be performed through an intermediate, not directly.
P.S. Waiting for a such tool, I switched off the trackbacks for this blog. But commenting still work.