This isn't even a new thing. Slips have been passed around asking for estimated contributions on numerous occasions.
Really? When? (not saying you're wrong Apognophos, just curious)
Most churches that practice tithing only 'encourage' it, it's not generally mandatory, and usually anonymous. Similarly 'passing the plate' is not required giving, but both can place pressure on the Congregation member to give, a pledge does the same thing. Though I think atm what's most interesting about this system will be seeing what direction (if any) they take it in.