Google built something similar years ago--not a direct competitor to RapGenius, but rather a generic annotation platform for the Web.
Guess what? It's now discontinued: http://www.google.com/sidewiki/
It's not trivial to build annotation platforms that are both compelling and easy to use. Hat tip to RapGenius!
Guess what? It's now discontinued: http://www.google.com/sidewiki/ It's not trivial to build annotation platforms that are both compelling and easy to use. Hat tip to RapGenius!