LinkedIn has some commercial use limitations on search:
Basic Account: 100 profiles daily.
LinkedIn Premium Account:
Free: 100 profiles daily.
Business Plus: 500 profiles daily.
Executive: 700 profiles daily.
Pro: 1,000 profiles daily.
For reading commercial use limitations on LinkedIn click
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LinkedIn also blocks user accounts/IP address if too many requests are fired within a certain time limit. For example 150 - 200 requests in 2 - 3 minutes.（公用爬墙或许也会遇到这样的限制）
LinkedIn provides Email address, Phone, Website, Address of the connections for all your first degree connections but in case of second, and third degree connections, email addresses will be available only if LinkedIn member has made email address public. Same will apply to your out-of-network connections.
