Retailing tycoon John Wanamaker famously said that half the money he spent on advertising was wasted — he just couldn't tell which half.

A century later, a shirtless stud has once again prompted debate on how to judge the effectiveness of marketing communication.

By all accounts, the Old Spice Guy has been a huge hit. The campaign, starring a well-muscled former NFL scrub named Isaiah Mustafa, began with a series of TV commercials that went viral after posting on YouTube.

Millions went online to see the humorous spots, created by Portland, Ore., agency Wieden + Kennedy. But the campaign really took off in mid-July, when Mustafa filmed nearly 200 videos in less than a week, responding to fans' questions and comments posted on Twitter and other social networking sites.

Here are his video responses to TV star Ellen Degeneres, Olympic speed skater Apolo Ohno and political strategist-turned-pundit George Stephanopoulos. But he also responded to questions from regular people, such as this YouTube commenter.

Results of the campaign to date:

• Nearly 100,000 Twitter followers for Old Spice

• More than 675,000 Facebook friends

• More than 110 million viewers for all the videos combined

A home run, right? Not so fast. Some analysts are questioning whether the admittedly huge response has actually translated into increased sales for Old Spice products.

One noted that the run of social media activity corresponded with a heavy dose of discounting and couponing, suggesting that those old-fashioned techniques actually may have carried the marketing load. Others pointed out that competing body wash products had also posted significant gains — without Old Spice's social media efforts.

I'll let the insiders at Old Spice and its competitors pore over the sales figures. What I'd say is that any campaign that puts up these kinds of numbers is an unqualified success.

Yes, the bottom line is sales, but men don't run out and buy a new bottle of after shave or body wash just because they saw a commercial. But of the millions who have viewed the Old Spice content, surely some will give it a try the next time they run out of their usual brand.

And let's not forget one additional piece of genius in this campaign: it's selling a men's product by explicitly pitching it to women, who probably do most of the actual buying of grooming products for their menfolk. Several of the video spots start with the greeting, "Hello, ladies." Again, women who have seen this campaign are certainly more likely to toss some Old Spice in their shopping carts.

This campaign is a major step in repositioning a tired brand, a process akin to turning an ocean liner. I'd say the effort is off to a fantastic start.