atDNA can be a *great* help with brick walls when you are able to compare segments (something on the priority list for 2013, according to Ancestry).
For example, over at 23andMe I have a few DNA matches who all descend from a John Smith (I wish that was a pseudonym!), and we all match each other on the same segment. If I find another match on that segment who also matches my other matches, I can tell them, "Hey, looks like you're a John Smith descendant." (Or else one of his ancestors.) Maybe that will help bust down a brick wall for them after they look at where John Smith lived, his daughters' names, etc.
If Ancestry wants to *really* jump ahead of the competition, they should not only give us segment comparison, but also give us the ability to label a chromosome map to show ancestors associated with particular segments (with some extra options for phasing and speculation). Oooo... dusting off the Beta Feedback button! ;)