MPL 1.1 talks about
"such Participant's Contributor Version directly or indirectly infringes any patent"
Which refers to the software itself. Which means it's a patent retaliation clause similar to the one Microsoft and Google use. If you claim patents on someone for using specific software, you lose any patent licenses for said software that were granted to you. But in Facebook's case, the retaliation extends when you make any patent claim on anything Facebook does, even if it's completely unrelated to the software in question. Meanwhile, the patent license that Facebook gives you does not extend beyond the software in question.
So you're effectively licensing all your patents to Facebook, and Facebook only gives you the ones you need to use the software.
MPL 1.1 talks about "such Participant's Contributor Version directly or indirectly infringes any patent"
Which refers to the software itself. Which means it's a patent retaliation clause similar to the one Microsoft and Google use. If you claim patents on someone for using specific software, you lose any patent licenses for said software that were granted to you. But in Facebook's case, the retaliation extends when you make any patent claim on anything Facebook does, even if it's completely unrelated to the software in question. Meanwhile, the patent license that Facebook gives you does not extend beyond the software in question.
So you're effectively licensing all your patents to Facebook, and Facebook only gives you the ones you need to use the software.