Why doesn't the Oracle RDBMS feature in the web space?

There was a recent post by Nati Shalom analyzing Why most large-scale web sites not written in Java based on a statistics from Pingdom on What nine of the world’s largest websites are running on.

Assuming the Pingdom analysis is correct, there is a glaring whole in the database technologies category used by major websites; Where is Oracle?

Geva Perry picked up on this in his post Where is Oracle?. There are a number of other follow up posts within the blogosphere, but unfortunately mostly have degenerated into personality clashes, protecting personal agendas and the usual large corporation bashing; you can follow the trail if you so desire.

But the question is still valid and seems to have passed the Oracle blogosphere by in the last few month possibly thanks to OOW (unless I missed it of course). Where is Oracle in the web space? Given that there is so much publicity about the Web 2.0 world and innovation making it an important market at the moment, why doesn't the Oracle RDBMS feature in that arena? Many of us claim that the Oracle RDBMS is a very sophisticated product, but why is the apparent market leader in RDBMS technology not adopted as the RDBMS of choice by web companies?

Maybe it's a question of ongoing cost. MySQL and the LAMP stack are free.

Maybe these web companies came from the "start-up" mold, were experimental to start with, and as such the reliance of free products from day 1 was imperative to get their products and services out the door?

Maybe it's a question of open source, and the ability to rewrite and debug the entire stack?

Maybe the Oracle RDBMS is overkill for the database requirements of most websites?

Or maybe the analysis is just plain wrong.

What's your opinion of why the Oracle RDBMS is missing?

Footnote: You'll note that there are some obvious missing web companies in the Pingdom analysis, including Google, Yahoo etc.