QUOTE
...in 2010 we began to see indicators of banner and Jimmy fatigue expressed in mainstream and social media. We interpret this as a warning: we expect donations to
continue strong growth, but a ceiling may be coming into view. And we will need to find alternatives to over-utilization of Jimmy, in order to preserve his appeal.
...
QUOTE
During the 2010 campaign, the Wikimedia Foundation began to
see the Jimmy appeals gently mocked by media and the general public. The
mockery was mostly affectionate but still: people's goodwill towards Wikipedia
is not unlimited, and the fundraiser is inherently annoying.
Translation: work out on your jimmy too much and you'll go blind.
Edit: Ninja'ed by EricBarbour.
This post has been edited by Zoloft: 
"Jimmy fatigue"
thekohser "Jimmy fatigue" 
