CafePress vs Zazzle Website Traffic

I was doing some research on Alexa.com and decided to see what's new in the CafePress vs Zazzle battle.  I was kind of surprised to see what the website traffic picture looks like these days.  While Zazzle isn't doing all that much climbing, the two seem to be headed for a neck and neck race since CafePress's traffic is obviously on the decline. What this means? I'm not 100% sure. what I'm more interested in is why CP's traffic seems to be tanking over the last few months?