150 million requests per day is just under 2 requests a second... 100k users/shard is also hardly impressive even if you account for 2x or 3x replication.

I hate to sound like a dick, but anyone who has dealt with large scale web apps would consider this a starting point, not worthy of a architecture presentation.

EDIT: Ah ha. Having never used Evernote before, they didn't make it very clear that they are essentially trying to build a SAN. I assumed they were storing plain text notes like stickies.