BIG installations of PostgresQL?

Hello,

My company is looking at two very large DB vendors to bear most of data
burden of our company; however I'd like to propose PostgresQL to handle
some of the tasks, specifically a large number read-only search DBs.
Postgres already has the win in terms of features and it's now down to
risk.

Many of the other folks at the company feel an open-source DB is more
risky because it is less well tested compared to commercial
counterparts. I'm looking for examples of large installations of
Postgres with huge data sets, high traffic volumes, high update rates,
etc, particularly large, recognizable names. I know you guys get this
question a lot, but can anyone share experiences with using Postgres in
large settings with huge query rates, replication, etc? Any stories you
guys can share (in public or private) would be greatly appreciated.
Thanks in advance!

Logan Bowers