Editor's note: Pete Cashmore is founder and CEO of Mashable, a popular blog about social media. He writes a weekly column about social networking and tech for CNN.com.

(CNN) -- Google is working on a social service to rival Facebook, if Web rumors are to be believed.

And while Google's social-networking efforts have so far fallen flat, even satisfied Facebook users should hope that the search engine's efforts bear fruit.

First, to the rumor: A now-deleted Tweet last weekend from entrepreneur Kevin Rose claimed that Google is working on a Facebook competitor called "Google Me."

That claim gained credence as former Facebook CTO Adam D'Angelo weighed in. Posting a response on the question-and-answer service Quora, D'Angelo wrote: "This is not a rumor. This is a real project. There are a large number of people working on it. I am completely confident about this."

Google, he added, is threatened by Facebook's rise to prominence and feels the need to build a social network of its own.

The Facebook threat

The search giant has legitimate cause for concern. As I wrote in this column two months ago, Facebook is gathering masses of data through its recently launched "Likes" feature, which lets Web visitors express interest in a piece of content.

More than 50,000 websites implemented this "Like button" in the week after it launched, providing Facebook with a treasure trove of data about the preferences of Web users. This data could form the basis of a powerful search engine, ranking Web pages by "Likes" rather than the links that Google relies upon.

What's more, Facebook could serve up different search results to each user based on the preferences of his or her friends.

It gets worse for Google. Facebook's mountain of personal data could also provide the backbone of an ad network many times more targeted than Google's keyword-based advertising. If Facebook were to launch both a search engine and ad network, it could put a significant dent in Google's more than $23 billion in annual revenue.

But Google shouldn't be the only party concerned about Facebook's rapid ascent -- the lack of a Facebook alternative is a threat to consumer choice, providing no escape route when things turn sour.

No real alternative

Facebook's privacy issues over recent months have opened our eyes to a grim reality: There is no real alternative. While dissatisfied MySpace users hopped over to Facebook, there is no truly competitive social network to which disgruntled Facebook users can elope.

The demand for a legitimate alternative is so great that a project called Diaspora was able to raise more than $200,000 from Web users to develop its "privacy aware, personally controlled, do-it-all, open source social network."

Until such a rival emerges, Facebook has little incentive to maintain user trust -- the only option available to unhappy Facebookers is to delete their accounts and lose contact with their friends.

Google's social stumbles

Alas, Google has a dismal track record when it comes to social networks. Orkut, an early social-networking effort, has seen success in Brazil, but in the U.S. it's virtually unheard of. Google Friend Connect, a possible rival to the recently renamed Facebook Connect, went nowhere.

Open Social, a challenge to Facebook Apps, has been forgotten. And Google Buzz, a recent attempt to add Twitter-like status updates to Gmail, flopped -- and generated a regrettable privacy backlash for the company.

Google, the narrative goes, is exquisitely talented at solving problems with algorithms. But when it comes to the touchy-feely stuff -- like human interaction -- it falls flat.

Getting behind Google

So while it's definitely a long shot, it's time to rally behind Google. If the search giant is able to pull off a half-decent Facebook rival, the fast-growing social network will finally have a competitor to keep its power in check.

That would be a win not just for Google, but for the Web as a whole.

The opinions expressed in this commentary are solely those of Pete Cashmore.