Twitter started with 4 founders.
Tumblr currently has 50 employees.
Instagram was developed by 2 people.
Foursquare has employed 70 people.
Posterous got 9 employees.
Dropbox was first coded by a single person.
Bitcasa has 5 people working on it.
Kiip has 15 plus their 19 year old CEO.
They have few people working but still considered as successful. Then it is not about the workforce.