A not-quite-perfect mockup of the Facebook "like" button. Credit: Wikimedia Commons.

Amid a strong quarter in which the social network saw mobile usage zoom to new highs, Facebook (NASDAQ:FB) is testing new ways to keep you engaged with the site.

Two experiments, in particular, should have Facebook investors interested. First is a "buy" button that gives users who "like" a product the ability to buy it from within a newsfeed. Second is a "save" button for squirreling away content that is interesting but which you'd rather return to at a later point. Both features could get users back on the site more often.

A well-timed trial
The timing couldn't be better. Facebook's operating income more than doubled in the second quarter on a 61% increase in revenue. What's more, the company is on pace to generate significantly more cash flow from operations in 2014 than is needed to run the business -- $5 billion at the current pace. CEO Mark Zuckerberg and his team have plenty of capital to try new things.

And they have good reason to do so. Recent Forrester Research findings conclude that teens are not only coming back to Facebook, they're also more likely to engage with mobile ads. A sharp increase in the company's advertising revenue from mobile devices in the second quarter speaks to this trend. In that quarter, Facebook derived 62% of its advertising sales from mobile devices, up from 41% in the year-ago period.

The "save" button could boost those numbers by making it easier for teens and other users to engage with a variety of content shared on the platform.

Meanwhile, the "buy" button could help win more business from independent workers and small businesses. Authors, for example. Amazon.com (NASDAQ:AMZN) has taken a PR hit over stingy payment terms for self-published works available via the Kindle Unlimited streaming service. Authors seeking better terms could do well adding the "buy" button to a Facebook page, spurring sales to fans who "like" their work.

What to do now
At least that's the theory. For investors, the takeaway here is that Facebook isn't satisfied with its current mix -- even as it produces hypergrowth in key areas of the business. That's a good sign. And yet, with a market cap of $192.5 billion and trading for 97 times trailing earnings, this is no cheap stock. So if you buy here, nibble. Add a bite at a time while taking advantage of short-term sell-offs.

All signs point to Facebook as a stock worth owning for the very long term. There's no need to rush a buy, especially with enthusiasm taking the stock to record highs.