You gotta love scaling stories.

1. S3 rocks. (I knew that)
2. Use YSlow and Firebug to set HTTP cache control (and Gzip everything).
3. Just go with InnoDB (unless you need specific MyISAM stuff, which you probably don’t).

Of course they talk a lot about all the mongrel scaling crapp that Rails needs that we don’t have to worry about with PHP :)