I unlocked the 100 flags the other day, I have just been joining Cruise and proposing a basewar challenge on river rush (as JACA said it's shorter between flags than Highway 101)
I've moved on to steals now, which might well be easier on H101 though as it is narrower, less room for your opponents to get out of your way.
EDIT: Steals unlocked tonight, mid cruise basewar game just after I'd taken the flag off someone on the other team, so I can confirm it has nothing to do with "saving" (aka returning) your flag. I just waited at my flag and chased after anyone who picked it up. I had been returning them but thought I might save you that effort by sharing on here.
Last edited by LeiChat; 02-17-2009 at 12:31 AM.