Bzzzt! That's the fail buzzer.
"What I meant to say is that MySQL "legitimized" the use of Postgresql in the corporate world. MySQL had a great marketing machine to sell something crappy. Now people realize they can use an open source database and Postgresql is the better technology."
No. Know how I know this ? Because I was prototyping corporate SaaS systems built on PostrgreSQL long before the web kiddies started beating their chests about MySQL.
"Regarding your Windows system - what is it doing ?"
Systems. Plural. But to pick just one : running a multinational pharmaceutical company's entire operation from document management, through mail, through ERP, through warehouse and logistics through monitoring and real time production in factories.
You need to get a dose of reality here and understand that some very large shops run end to end MS kit.
"Or is it a complex, custom system running a stock exchange ? Is it running SAP ? I guess it's not."
I bet you've got the slashdot post about the LSE switch to Linux printed out - with all the comments - and hanging on the wall of your room at your mummy's house, probably all neatly arranged around your candle-lit Stallman shrine. But then again, Direct Edge, Karachi, Bovespa.
You seem to be under the impression that there are no large volume trading systems that aren't based on Linux, once again if we compare your imagination with reality we see there are some large differences.
Linux is unquestionably a good OS and has scored some seriously impressive real world wins, and I have no doubt that it will continue to do so, but your assertion that MS does not, can not, and will not play in these same markets simply doesn't hold up to examination.
And by the way, you do know that you can run SAP on Windows ? With SQL Server as a backing store ? You knew that right ?