Hi all -- I've seen this topic come up a couple of times, so I just thought I would mention our experience at work running boxes without swap:
We run caching webservers without swap--there are reasons, but they're rather technical (pm me if you really wanna know). We have a lot of them so if one craps it's no big deal. That said, on the rare occasions when a box runs out of ram it will lock hard, requiring it to be power-cycled to recover.
In our case, when a runaway app locks a box we are not at risk of data loss. That might not be the case for you.