Avantages
Job security is high due to the recession proof nature of eBay's business. Many of my colleagues have been working for eBay for almost a decade and if you are willing and able to follow along you too will be able to enjoy a long career with the company without having to worry too much about how the economy is doing.
Inconvénients
It's not what you know, it's who you know. There is little correlation between a person's value to the business, i.e. relevant skills or education and their level of compensation and benefits. Oftentimes, responsibilities are given to people lacking the expertise needed to fulfill them properly. This leads to bad hires who then clog up the gears and keep more deserving people down or out. To succeed it is also necessary to be able to deal with the preponderance of MBA type employees, all of whom have a strong tendency to be on the vapid side of things. Talking BS and acting important will get you much further than delivering actual substantive improvements to the business itself.