The problem is folks, as soon as you get a large number of users every compromise you made by using a toy language or database is magnified 1000 times. Google didn't implement in some scripting language to get to the market a few months early.
----------------------------
Some Rough Statistics (from August 29th, 1996)
BackRub is written in Java and Python and runs on several Sun Ultras and Intel Pentiums running Linux. The primary database is kept on an Sun Ultra II with 28GB of disk. Scott Hassan and Alan Steremberg have provided a great deal of very talented implementation help. Sergey Brin has also been very involved and deserves many thanks.
-Larry Page pagecs.stanford.edu
----------------------------
There's something to be said about rapid prototyping and evaluation.
I don't believe all companies can survive with a python or ruby solution. I do think that, as technologists, we worry too much about the "optimal" solution to technical problems when, in most cases, businesses are made or lost in people problems. People problems are really hard because there are few "right" answers. Instead, it is an optimization game, and optimization games require agility.
If you are that amazing at C or C++ that you can iterate amazingly quickly with them, then use them! That will give you a leg up later. I've been developing software for 15 years and have use everything from C and C++ to Java to Python to Objective C; and I've seen a massive difference in my ability to iterate with each of them.
Optimize for what works best for you, but don't be surprised if you choose C++ and a competitor who doesn't care about the "perfect" solution runs circles around you in the market because they chose something different (even if they re-write in C++ in 10 years, after they've stolen all of your customers).
That's actually exactly what they did.