To my mind, a write in vote for Spongebob or "None of the Above" (or "No Confidence") is worse than not voting at all. Someone voting in that manner is expressing a displeasure with a perceived cynicism in out political system, and doing so in a completely cynical way, thereby perpetuating the problem, rather than working to solve it.
When I was at university, elections to student union bodies were done by proportional representation. You voted for your favourite, second, third etc.
As part of that, every election included an option on the ballot to re-open nominations ("RON"). If you didn't like the available candidates, you could vote RON as any of your preferences. If enough people voted for RON, the election had to be run again right from scratch.
(There was one election where only one candidate stood for a post, and some friends and I realised they were not up to the job, so we ran an election campaign for RON (every candidate got the same publicity budget, and RON counted as a candidate!). Given this was the late eighties, guess who ended up on all the "Vote RON" posters?)