I would point out that global replication is one of the things that makes CouchDB's master-master replication so tasty.
You can't accomplish the same thing with Mongo in a R/W environment since you can only write to the master in a replica set. You could have multiple read-only slaves in other geographical locations, but that isn't always helpful.
You can also somewhat fake it with a much more complex mongo-replica-set-per-region sharding configuration, but then you don't have the same data available in each region in each replica set.
PostgreSQL in 9.1 added master/master streaming replication which is nice. Not sure what MySQL does in these situations.
This is one of the biggest failings of SimpleDB that I think keeps it held back from being a huge success, the region dependency of it and the seeming lack of support from Amazon (the only product whose forums frequently go a week without a reply).
Had SimpleDB has an optional global redundancy for quick read/writes in all locations, I think it would have been the killer product a lot of people were looking for.
Instead I have to roll my own with a fully connected CouchDB graph of servers. Ahh well.
"EIBs"?
I would point out that global replication is one of the things that makes CouchDB's master-master replication so tasty.
You can't accomplish the same thing with Mongo in a R/W environment since you can only write to the master in a replica set. You could have multiple read-only slaves in other geographical locations, but that isn't always helpful.
You can also somewhat fake it with a much more complex mongo-replica-set-per-region sharding configuration, but then you don't have the same data available in each region in each replica set.
PostgreSQL in 9.1 added master/master streaming replication which is nice. Not sure what MySQL does in these situations.