Some thoughts on the orange checkmark:

Still the best way to improse a real world cost on spam by collateralizeing usage by bitcoin.

But there might be a way to include aspects of a web of trust to or skme form of reputation by adding the ability to put up collateral for someone else. This way you can "vouch" for someone you know in a way that imposes a cost if the person who you vouched for fails.

There might also be a way to take away your collateral if you no longer wan tovoucbh forhimm.

Doesnanylne know if there's a project like this already?