But he has so many better options. He could listen to his userbase and create a product they enjoy. Then explain his cost and ask for donations on the site (with a progres bar as wikipedia does). If you have goodwill in your userbase, you could even just ask people for money in a monthly fashion and give them some "Reddit Supporter" badge. Maybe a "Reddit Supporter" can then vote on the functionality that will be implemented in reddit.
If he'd communicate it well, he could even monetize the API fairly (let's say 1-2x the ad revenue he would get with similar traffic) or monetize it on the user side (user has to pay e.g. $10 for yearly api key).
I can say for myself I'd be more than willing to donate to reddit if they asked for it and I had the feeling they were actually trying to listen to the userbase and improve the platform.
With his current behavior he's just destroying any good-will of the userbase and therefore any direct monetization potential.
I wouldn't be so excited about this spike. I feel it may have been created by a botnet auto creating a bunch of accounts on 18th and 19th. It doesn't look natural.
edit: You can also see the "active user ratio" dropping significantly in the same timeframe.