Loss of Stumbleupon traffic

???????

I am not sure what have been happening with Stumbleupon recently.  I have been using it advertiser service to drive traffic to this here blog ($0.05 a click seemed like quite a good deal, and I feel that surely someone must want to read what I have to say!).  However in the last week the amount of traffic has dropped to zero for no given reason.  Perhaps there is just not enough traffic to go round?