Absolutely wrong.

We use Dell 2950's for our DB nodes in our Oracle clusters. Biggest one right now is 12 nodes.

And if it scales, but costs too much (a relative concept at best), then it somehow doesn't scale any more?

Of course cost matters, and it comes down to what your application requirements are, and what your revenue model is, and your risk management requirements are, etc., etc.

If you want to talk technology only, it's a no-brainer.

If you want to talk cost and context-appropriate implementation of technology, then provide a detailed context, not generalizations.

Again, you're not going to see an online bank use CouchDB as their back-end, and likewise, you're not going to see a relatively free service use stupidly expensive technology.

How much data, and with a SAN? How much did the SAN cost? What kind of data?

But yes - if its too expensive to do, that means it doesn't scale well. Since when does money not matter in everything? The entire point of all of this is to use commodity PCs to achieve linear scalability cost-effectively, and to escape relational structure for data ill-suited to relational schemas.

I don't think anyone is suggesting an online bank should not use existing commercial databases and SQL.

It's one thing when we're talking about facebook. It's entirely another matter when we're talking about a large bank. Do you want your bank to use mysql to store your financial data?

Regarding the importance of money, look at the existing infrastructure in financial institutions. They spend millions of dollars a year on mainframes from IBM. The cost of oracle compared to this is relatively low.

We're talking about two entirely different markets and applications of "databases" here. The claim of SQL db's not scaling is not true.

You know what's funny... no ones talking about a bank but you. For most apps built by most startups, Oracle is absurdly expensive, so yes, it doesn't scale well.