High Scalability Building bigger, faster, more reliable websites.

While I agree with you on cost, very probably even tco, there is no denying Oracle does a lot, if not all, of these things better/faster(/stronger).

They also have a valid point stating the features that MySQL does implement, like partitioning, are still immature compared to their technology.

But in their efforts to minimalise MySQL's achievements and benefits they pitch a very important sales line:
"Facebook had to make 'improvements' to MySQL replication"
and
"Google had to significantly change MySQL replication to make it work"
Although the tone of these statements is negative, I don't see this kind of flexibility in their product!

I've not even read the paper yet, but the statement that "Oracle rules and MySQL sucks for sharding" is totally incorrect and biased.

Sure MySql has some problems, however, many many large scale public websites use MySql with sharded databases.

I'd be interested to know of a large scale public website which can afford to use Oracle.

Hmmm....
Seems that all of those points are also features of Postgresql, except replication.

Who is the audience of this paper?

There is no denying that Oracle enterprise-edition database is rock-solid, I use it daily and it consistently delivers. It's also $48k per processor (2 cores) at list price (expect a 25%-50% discount) for a perpetual license and a 18% annual support fee. Note that it went from $40k to $48k last August, wonderfully timed with a slowing economy.

So either you have deep pockets, in which case you're probably already an oracle customer and you don't mind spending a lot of money on licenses; or you're a small, growing company that needs to accommodate the addition of new servers often and would rather save cash and spend more time on operations and run mysql.

Unless Oracle significantly changes its licensing model the argument that Oracle is better for sharding is a very tough sell from a business standpoint. And within 5 years chances are, the RDBMS will be completely commoditized, just as the OS market ended up.