If you use ^C to get a lazy repository, darcs will forget that you asked 
for a specific tag.

GOOD:

$ darcs get --lazy --tag 2.0.0 http://darcs.net
This is the darcs darcs repository.
**********************
Directory '/home/lane/src/darcs.net' already exists, creating repository 
as '/home/lane/src/darcs.net_1'
Unapplying 105 patches.
Finished getting.

BAD:

$ darcs get --tag "2.0.0" http://darcs.net
This is the darcs darcs repository.
**********************
Directory '/home/lane/src/darcs.net' already exists, creating repository 
as '/home/lane/src/darcs.net_1'
Copying patches, to get lazy repository hit ctrl-C...
withSignalsHandled: Interrupted!

Thanks for the report.
Sounds like a relatively easy to fix. Takers?