The popular social network StumbleUpon has lost a lot of steam when it comes to referral traffic. Since January 2009, Stumble Referral traffic is down by more than 66% according to Google Analytics. Back in January 2009, our friends and subscribers were close to the same numbers today, but under a different account.

I know some people may say that your friends hardly have any subscribers, but that is not the case. Of the 100 friends, more than 30% have more than 150 subscribers and 20% have at least 50 to 100 subscribers.

Why has the referral traffic from StumbleUpon fallen off? I know this has nothing to do with the original owners buying back StumbleUpon from eBay. It’s hard to figure out why the referral traffic has dropped off, but it has significantly. Here are actual analytics from January 2009 compared to June 2009.

January – stumbleupon.com (referral) 15,524

June – stumbleupon.com (referral) 5,007

The chart below suggests that StumbleUpon Unique Visits is up 16.7% over the last 3 months.

I am not concerned that StumbleUpon traffic has slowed because our Google Organic traffic now makes up more than 48% of our total traffic. This means we are doing well when it comes to search engine traffic.

I was excited when StumbleUpon created the share tool, but it really hasn’t made an impact when it comes to referral traffic. The share tool really makes it easy to share a link with all your friends with a couple of clicks.

There’s no way I am giving up on SU as it brings in more than 5,000 visits per month, but I wish I knew why the referral traffic has dropped off. Did StumbleUpon make a change in their system? Who knows, but I am sure someone will figure out what’s going on.