LinkedIn has 150 million professionals on its network compared to 730 million email addresses. While email has more users, LinkedIn allows professionals to connect through relationships and build a global professional network of over 900,000 relationships between nearly 18,000 users, whereas individual email networks tend to be smaller with around 55,000 users and 6.7 million relationships.

1. LinkedIn vs. Email: Global Network
LinkedIn Email
150M Professionals
Source: http://press.linkedin.com/about
730M Professionals1
Source: http://www.radicati.com/
= 10M Professionals
1
Number of Corporate Email addresses only

2. LinkedIn vs. Email: The TR Network
LinkedIn Email
17,862 Users 55,000 Users
900k Relationships1 6.7M Relationships
1
Assuming average number of 1st degree relationships is 50:
http://www.linkedin.com/answers/using-linkedIn/ULI/495289-927061