As a hiring manager, my focus is whether or not the applicant is able to do well in the position. I've never really concerned myself with the online presence of the applicant. I look at rummaging around in google to check out an applicant as more or less equivalent to hiring an investigator to do a background check. The fact that googling is easier and cheaper than hiring an investigator does not change the motive for doing so.
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An exception would be if the applicant links to his professional online presence in the CV. Then I would use that as I would any other information on the CV. However the presence on the web does not make the information different than having the same information on the CV.
If I were hiring for a sensitive position where a background check is warranted, then I would do a real background check.
But if no background check is required, why go poking around in someone's private life.