Haha, my work colleague just mentioned this to me. But she said she was disappointed that people were only pledging to eat 1 banana (or 1 a day, I can't remember) because she sees me eating a massive narna smoothie every day, so she knows a person can eat many more than 1 a day and be healthy :-)
The original intention was to organize an event where 1m bananas will be eaten by 10k people, 100 each.
It was then interrupted by some doctors who told that high amounts of potassium, which bananas are rich of, may be fatal.
That's why they don't recommend guzzling down too many bananas.