If you've ever had facebook preview an old version of web page, here's a solution. You can use this fb developer's tool to "force" fb to "scrape" a URL and cache a new preview.
A few days ago I was posting a link to my own web page, and discovered that the title of the page was incorrect - from another page I'd used as a template. But even after I changed the page on the web server, and even on a different computer, fb persistently pulled up the old cached title. I've had this happen a few times before, and never looked for a solution until now. This is great.