It definitely explores the dark side much more (ie: The tagline is 'you don't make it to 500 million friends without making a few enemies'), but there are parts where I found myself laughing out loud. Seriously, Sorkin wrote those parts for Eisenberg and Timberlake. Envisioning some of those lines; it's just too perfect.
Totally agree with you. The script is definitely dark, but the comedic stuff is absolute gold. And totally back you on the casting as well - perfect choices