In general, I wrote this article in order to synthesize some news from the last month which had come in about migrations from MySQL to PostgreSQL in the web developer world. EngineYard was featured because (a) it's recent news and (b) EngineYard had, historically, been a very adamant MySQL-only shop. I expected it to be generally interesting, in the same way that it would be if Yahoo migrated from FreeBSD to Linux.
To the extent that I failed to convey that, my apologies. This is my first time writing this kind of a piece, and it's a bit of an experiment for LWN as well. We'll take the criticism into account in adjusting the next article I do which contains an interview. This article went through 5 drafts, BTW.
To be completely clear: I wrote this article as a paid writer for LWN, and did so because I believed that it exemplified changes in the open source database world which would be interesting to readers, and the LWN editors thought that it would be as well.