You shouldn't! Ripple users need to use the same level of care and discrimination choosing a gateway as they do in choosing an exchange (I think the wiki makes the clear, at least...I hope it does!)

There's significant overlap between gateways and exchanges. A Bitcoin exchange makes the perfect candidate for a gateway since they already perform the same functions. Ripple uses the term "gateway" as opposed to exchange because a gateway does more - it's IOUs can be traded in a decentralized fashion. Note that I'm not saying that the gateway itself is decentralized, they still represent a server where activity takes place (i.e. web interface to your Bitstamp account). But the IOUs are (there's still counterparty risk though).

Anonymous gateways are a bad thing! You want to make sure that you use a gateway which is a registered business, preferably in your jurisdiction. They should also have a good reputation.