Note that "client supplied identification" is being pushed for AML/KYC
compliance, e.g. Netki's AML/KYC compliance product:

http://www.coindesk.com/blockchain-identity-company-netki-launch-ssl-certificate-blockchain/

This is an extremely undesirable feature to be baking into standards given it's
negative impact on fungibility and privacy; we should not be adopting standards
with AML/KYC support, for much the same reasons that the W3C should not be
standardizing DRM.

KYC isn't the only use case. There are other situations in which you would want to confirm who is sending you money. Making it *required* would of course be a horrible idea, but allowing people to identify themselves, in many cases with an online-only identity that isn't tied to their real world identity, will be very useful to newly-developing use cases.