A few months ago, I was checking the list of referral sources for my blog when I noticed that StumbleUpon was high on the list, sitting quietly among more recent networking superpowers like Pinterest. I was surprised — the last I'd really heard from StumbleUpon was back in 2007, when it had gained enough popularity to garner a big payday from eBay. Soon after that, the appeal of that particular "discovery engine" waned and I, like many others, abandoned that toolbar for other online distractions and yet, it remains a viable entity. I began wondering about the other once-great social media giants. Here's a brief rundown of how some of them have evolved since their heyday.

MySpace

Once: From 2005 to 2008, MySpace was our Facebook before "Facebook."

Now: During the decline of its social networking function, MySpace realized it still had prowess in one particular area — music. As more and more users walked away from their once carefully tended personal profiles, they continued to return to hear new tracks from the pages of their favorite independent musicians. Soon, video channels followed suit and then the record labels arrived. It wasn't long before full-scale advertising campaigns covered every available surface. After a series of layoffs and a continual decline in users, MySpace was "relaunched" as a "social entertainment" engine. In June 2011, it was purchased by Specific Media and Justin Timberlake for $35 million.

Ning

Once: The future of social networking is to just create your own network — or two, or twenty.

Now: In 2008, Ning's appeal existed initially in "fringe groups" or people who were interested in creating their own topic-specific communities complete with photos, blogs, and video sharing capabilities. A sample community site would be one dedicated to the television show Lost where likeminded friends could congregate. The company has since evolved and the platform now draws more marketers and community organizers than the Average Joe who wants to start a social networking site around the films of Vince Vaughn. Ning's most recent milestones include a lucrative acquisition by Glam Media for $150 million in September 2011.

StumbleUpon

Once: Glued to browsers everywhere.

Now: We may not be talking about StumbleUpon in our everyday circles, but the number of "stumbles," which hit 25 billion in August 2011, would suggest that someone, somewhere, is certainly still using it. As of October 2011, StumbleUpon reported having 20 million registered users; compared to Facebook's 800 million (Jan. 2012) and Twitter's 300 million (2011), it's still just a drop in the bucket. Chatter online would indicate that its biggest threat these days is new discovery engine and inspiration-generator Pinterest.