I'm not sure how you can say developing in a county adjacent to silicon valley is the same thing as developing in a country more than 3000 miles away.
If Silicon Valley is a metaphor then the term is meaningless. New York is Silicon Valley. So is Chicago. So is Vancover, and London.
If it isn't---because of the unique legal structure, cultural consciousness, and developer concentration in and around Silicon Valley---then its unfair to say that a Luxumburg company operating under EU rules is a silicon valley company.
Also San Jose has called itself in the past "the capitol of Silicon Valley".
Perhaps they felt Silicon Valley was a SF bay area mindset rather than a specific geographic location.
When I was a kid, San Jose was the "gateway to Silicon Valley" which basically was anywhere in Santa Clara county (at that time, mostly the 415 area code).
Frankly it would seem that analysis of the stock vesting expectations of hackers in Tallinn is more relevant to the story and the structure of the Silverlake partner agreement than the expectations of Silicon Valley programmers when it comes to attracting and retaining technical talent at Skype and among the people mentioned in the techpress, it has been difficult to find any in key technical roles.
Stock vesting expectations of hackers in Tallinn is not any different than in any other part of the world.