Annie Scranton has a little problem. The founder of a public relations firm is a sober-minded individual, but when it comes to this one thing, she has a definite compulsion. It's the "Like" button on Facebook -- she just can't stop clicking it.

"I'm totally obsessed with it," says the 31 year old. "Just like a lot of people I know. My friends and I call it 'Like-Bombing', where you go online and like everything."

So it's a good thing for serial "Likers" like Scranton that there are more and more rewards for consumers who click that button, writes Chris Taylor,  a Reuters columnist.

Hotel chain Marriott, for instance, is currently offering prizes totaling 10 million reward points for those who Like its Facebook pages, including two grand prizes of a million points each.

Think of it as a social-media arms race among corporations, to see which can amass the greatest number of online followers.

"It's become a real competition between companies to grow the size of that number, and to have more fans than your rivals," says Matt Simpson, marketing director for Phoenix-based Bulbstorm, which develops social-media apps for companies such as NBC and World Wrestling Entertainment.

"Over the last year, we've been seeing more and more of it, and it's been driven largely by promotional applications like sweepstakes."

If you "Liked" Toys 'R Us before Thanksgiving, for instance, you got a shot at a limo ride, a $1,000 shopping spree, and exclusive store access before its doors opened for Black Friday sales.

Travel site Expedia, meanwhile, hosted a 'FriendTrips' sweepstakes for those who Liked its Facebook page, offering voyages to one of 13 different destinations.

As a result, in the third quarter of this year, an average of 100 million "Like" buttons were being clicked on Facebook every day. That's double the amount of liking going on, compared with the same period last year.

Corporations are doing this for a reason, of course. They're building marketing lists, they're aiming to boost sales, and they're planting themselves in users' news feeds.

When Coca-Cola has more than 36 million Likes, and Disney has more than 29 million, they've assembled a ready-made audience that can be tapped at any time.

And here's a little secret: While companies are certainly happy to have you as a fan, what they're really interested in isn't you; it's your friends.

Because if you officially Like Starbucks, your friends see that you've liked Starbucks, and they become more likely to spend there as well.

"Friends of fans represent a much larger set of consumers than the brand's own fans," says Elisabeth Diana, Facebook's manager of corporate communications. "In fact they're 81 times the size of the actual fan base, so Likes are a way to reach those people as well."

The promotional pushes seem to be paying off.

Expedia's FriendTrips campaign, for instance, garnered 900,000 new Likes for the company. And while Marriott's contest is ongoing until the end of the year, its new Marriott Rewards Facebook page has already gone from zero to more than 170,000 Likes.

"We've surpassed all other hotel rewards programs in under three weeks," says Michelle Lapierre, Marriott's senior director of customer relationship marketing, taking a slap at rivals Hilton, Starwood and Hyatt.

Of course, once you have an army of online followers, that's not the end of the marketing road. Then there's the question of what to do with them all.

That's why companies are now proceeding to Phase Two of the Like operation: Figuring out how to engage and entertain consumers on an ongoing basis, with a flurry of polls and quizzes and games.

"Collecting Likes by giving away prizes is a great way to build a fan base, but it's not the be-all and end-all of Facebook marketing," says Bulbstorm's Simpson, who himself won a 10-day trip to Hawaii from just such an online promotion.

"Savvy brands are starting to focus on things with more entertainment value, to keep you around longer than the seven seconds it takes to fill out a form."

Beware, though, that Liking something publicly makes companies keenly interested in who you are and where you're surfing.

Not only that, but Facebook is rolling out so-called 'Sponsored Stories' of such activity. In other words, if you officially like Target's Facebook page, your friend Jim might get a Sponsored Story in his news feed announcing that thrilling development. So if you're uncomfortable with your personal business being public, then maybe Like-Bombing isn't your best online strategy.

"Facebook 'Like' buttons are increasing in prevalence across the Web, raising serious privacy concerns for those who value the privacy of their online reading habits," says Rainey Reitman, activism director for the San Francisco-based Electronic Frontier Foundation.

"This collection of information about one's Web browsing habits may violate many users' expectations of privacy. Our reading habits can be incredibly sensitive, and Facebook has a long history of playing fast and loose with user privacy."

Facebook reached a settlement with the Federal Trade Commission in November, agreeing to get users' permission before altering privacy settings and submitting to independent privacy audits for the next 20 years.

As for Pace's Annie Scranton, though, she has no plans to rein in her Like campaign - especially since it's brought her a number of new business prospects. So if you get Liked by her, don't be all that surprised.

"My business is inextricably linked to social media, so if I wasn't constantly Liking things, my clients wouldn't be happy," she says. "Even when I'm working, I'm on Facebook all day long. You can never do enough Liking." - Reuters

(The writer is a Reuters columnist. The opinions expressed are his own.)