I assume your company is not developing UX patents and the concern is more around developing a suite of products that use a FB library and dealing with unexpected costs or restrictions?
I would hate to avoid using what I thought were the most productive tools in anticipation of a very unlikely event. You'd essentially be paying a productivity penalty now, to try and avoid a productivity penalty in the future if you have to rewrite something.
The odds of a company like yours in a vertical getting sued by Facebook I would guess are vanishingly small.
Now if your core IP competes directly with FB I can see a little more risk because they could plausibly have strategic reasons to make your life difficult as well as a potential damages claim. However this would be a special case for only certain companies to worry about.