Just got the BrickPi last night! After getting it built and connected the first thing i did was to do a sudo apt-get update and upgrade to make sure i had the lastest and greatest weezy… before i could finish i ran out of space on /.
For anyone else that ran into a similar problem, the default image for weezy is 2gb, but the cards shipped from Dexter is 4gb. you can expand the rootfs and take advantage of all the space -
then select the option to expand the rootfs to use all available space on the sd card.
Hope this helps.