[spligak]

It isn't a problem if you're speaking specifically about Cloudant. They co-locate clusters next to your app as best they can (as Mike has mentioned elsewhere). That makes the network you're running on critical, however.

When we built out our message queue offering at SoftLayer (which uses Cloudant/BigCouch as a data store), latency out to the DB cluster simply never ended up being an issue. Properly leveraging DB features, I/O priority tuning, the caching tier behaving properly - all more often these end up being the culprit in performance issues.

What you need to better understand when considering a cloud-based data store is who's running your cluster. When it comes to guys like Adam, Mike and Robert, you're going to be very hard-pressed to find better (and available to you) talent in the CouchDB world. We certainly appreciate having them around.