Just finished reading some of the topics relating to concerns about the present and eventual size of the block chain.

Presently, the .bitcoin directory which contains the block chain is in excess of 600MB.  In my opinion, this is a non-trivial amount of disk space.  I among others have developed environments designed to assist with client security that involve running the client from a USB memory stick or other devices with resource limitations.

I read in one post, that it not necessary for every client to download/save the entire block chain in order to send/receive bitcoin.  Is a bitcoin client with this feature somewhere on the horizon?

Thanks for considering this issue and all your excellent work!

Matt