: weak as it is (or should be), think of a Klout score like certain IT certifications (A+, MCSE, etc.). It's s stand-in for a real measure. A cert (typically) only says someone passed. It doesn't indicate how well they did, or (for some certs) that it indicates how well they'll be able to apply their knowledge to any practical problem. That's the "impression" part you mention.
All the same, prima facie, as they only allow two of the numerous social networks, and no OpenID, for authentication, they're a joke (no LinkedIn, especially no Google, no Orkut, no identi.ca
, others). They've clearly therefore shown their bias for those two services and against all others.