It said to hit C-c if you want a lazy repository.  I did, so I hit C- 
c.  Then it gave me an error message.

zooko@deharo1:~/playground$ time darcs get http://allmydata.org/ 
source/tahoe/trunk-hashedformat
Copying patches, to get lazy repository hit ctrl-C...

darcs failed:  Couldn't fetch  
`0000001090-8268520b39ee453eb0cc01c820177703dfa9b704aeaa6ee4d66676806054 
46ed'
in subdir patches from sources:

thisrepo:/home/zooko/playground/trunk-hashedformat
repo:http://allmydata.org/source/tahoe/trunk-hashedformat
repo:/var/tmp/tm/tahoe
thisrepo:/home/source/darcs/tahoe/trunk-hashedformat-new
repo:/home/zooko
thisrepo:/var/tmp/tm/zooko
cache:/home/source/.darcs/cache

real    1m6.331s
user    0m18.930s
sys     0m4.250s