When using the tool, Stumbleupon on a slow work day and you have 'Stumbled' so many times that:
1. You are actually sick of the internet;
2. All the pages are beginning to look familiar;
3. You're clicking next out of habit and aren't even looking at the computer screen any more.
Lola: I had a slow day at work today, so I used Stumbleupon for 6 hours straight and I might murder something if I see another Cyanide and Happiness comic strip.
Roopy: Ouch, looks like you've hit Stumbleupon Saturation Point (SSP). Go read a book for a few days, you'll feel better.