Big no to ruby and asp.net
For a serious web facing business:
Php
Mysql
Python
1. Open source
2. Proven
3. Scalable
4. Availability of developers
Collocated on dedicated hardened secure servers and maintained by competent devs and sysadmins and you've got a robust and secure system.
Any one would shocked to know the true extent that the legacy financial system is hacked on all their proprietary commercial grade hardware and software.
So it's not necessarily the system / language that matters but the quality of the work of the individuals who implement your system
(And still your gonna get hacked if your system has any real value)