I think the author just made this up in an hour with some weak arguments.

No doubt LinkedIn is becoming very spammy from all the puzzles and (gasp) personal stuff like 'My son-in-law is having an operation, please pray for him'.

However, the value that most people derive from it and the ease with which you can ignore the spam will keep it being used until there is non-spammy, non-recruiter funded and 'open networking' alternate.