Pros
Fast growing. Influence (Good to see how our work relates to our daily life). Flat management (bi monthly CEO meeting). Relatively felaxible schedule (At least for my team). Good pay (compared with other industries, but I've got offers with higher pay..). Pay for working Sundays (Even though it is kind of mandatory to work one Sunday every two weeks, but you get paied and most internet companies still sometimes request employees to work on weekends but they don't pay). Free foods ( three meals, afternoon tea snacks, drinks and snacks).
Cons
Long hour? Well I am talking about China and I guess case in Silican Vally and LA could be different. Also, in China, most high-paying companies have long working hours...Some low paying ask the same.