It's an interesting idea, though a problematic one. I, personally, would rather they spent their profits on hiring more personnel, paying for a security audit, things like that ... The problem, too, with interest is ... What rate?
If you go by the rate most banks are giving on savings accounts right now, they could probably afford it but it'd amount to pretty much nil for most users. If someone argues they should go by, say, standard credit card interest because maybe someone couldn't easily pay their MasterCard bill on time ... That might be more than they could cover, realistically speaking.
I'm as frustrated as a lot of people -- I only had a portion of my coins there, I moved them to sell a few for more GPUs, then didn't have the opportunity thanks to my net connection dying before the transfer confirmed, and while I wouldn't have been destroyed if the coins had been stolen, it's been very irritating to wait this long to even find out that, yeah, my coins are still in my account there. But as far as compensation goes? I'd like to see them improve. A lot of people won't trust them after this, no matter what they do or don't do, or whether or not they pay out. If they reinvest into improvements instead of compensating us for perceived or actual losses, they're more likely to be good competition for other exchanges, which in turn pushes those exchanges to improve... and that benefits us all a lot more in the long run than a piddly week's worth of 1.5% APR.
By the way, if you were upset over $5,000, a week's worth of 1.5% APR means you get $1.56. Not a lot of money. Though if you multiply that around a lot of users and capital, and that could be the cost of a security audit or another programmer or a trio of customer service reps right there.