Companies are making an effort to sell products using social media.

Coca-Cola on Monday began letting friends send Cokes to each other through Twitter.

The Tweet-A-Coke promotion lets you tweet a link to a friend. Once your friend opens the link, it lets them order a Coke at participating Regal Cinemas locations.

To send the Coke, you have to authenticate your Twitter account and then enter your credit card information.

Coke is following in the footsteps of Starbucks, which did something similar last year.

Starbucks' Tweet-A-Coffee program used the same $5 limit. The Starbucks program prompted about $180,000 in purchases in its first month.

So, is social media commerce the wave of the future?

Facebook announced this month it started testing a "Buy" button that appears on ads and page posts from a select group of businesses.

Would you tweet someone a coffee or Coke? Or would you click the buy button on Facebook?