[Buggman]

Actually, the combination of "same-sex marrige" and polygamy could be abused hilariously: Groups could go out and create a vast network of interlinking "marriages" and then sue for spousal rights to whatever service they want to share.

Heck, I think all churches should immediately start working on that: "We're all the Bride of Christ, so we're all married, and you're discriminating against our religion if you disagree!"

That aside, just wait for the divorce statistics. They should be a source of great fun as well.

[Beagle8U]

A bisexual polygamist could marry an entire city/state.

That would make for a really cool form 1040 with millions of dependents, and a whopper of a rebate check!