Everyone should be running pg_basebackup + pg_receivexlog on a separate machine, preferably at a different data center.
These let you go back to any point in time. If you ran 'delete from orders where id=id', you can restore to the transaction before you ran that command.
If you are hosting your database on ec2, using only wal-e means that all of your data is hosted on amazon. If they were to cancel your service, you'd lose your data.
Running pg_basebackup+pg_receivexlog on a different provider is cheap insurance against that.
Be sure to test how fast wal-e can restore your data, btw. Restoring from s3 was significantly slower than restoring from a local disk (in my testing a while ago).
I ship wal logs to s3 for backup, and I do test restores on EC2.
What I've found is that most of the files can be grabbed really quickly, in the 3mb/sec range, but there's always a handful that run at 300k/sec. Running the downloads 8 or more at a time tends to help with that so that we're mostly maxing out the local network.
These let you go back to any point in time. If you ran 'delete from orders where id=id', you can restore to the transaction before you ran that command.
http://www.packtpub.com/how-to-postgresql-backup-and-restore... contains more information.
Also, postgresql 9.3 (out in a few months) supports disk page checksums which can detect filesystem failures immediately.