Your comparisons are not parallel. The article isn't saying LinkedIn contains a virus. The constructs "Linked grows with viral features" and "LinkedIn is a Virus" are much closer than you suggest.

I don't think the article meant that linkedin grows virally though. I think it was trying to compare linkedin to a virus that spreads by hijacking your address book.

At least that's how I read it.

The comparisons are not meant to be parallel. Try looking in context of the parent comment.