Seems to me that you want to be ambitious, but not crazy. The proposed project must be well within the constrains of reality - must be a hypothesis that can be actually tested that is - and must not ignore decades of well-established facts, just to foster some lunatic, crazy-ass idea that one may have.
The flip side to this is that there will be the occasional crazy idea that will be correct (prions come to mind right now, but science is littered with them - viruses causing cancer is another). Probably a simple rule of thumb is that imagination needs to be based on reality, and must be eventually verified by real experiments!
Some old ones Reposted...
8/18/13 - A Classification of PI's - find yours' in the list!
7/6/12 - Way to a "Science paper"
5/30/11 - 20/20 Hindsights
9/30/11 - Evolution of a bizzare, new Idea
11/17/2011 - Rationale for curiosty-driven research...
lessons from a 4 year old
1/28/12 - "GTFM" - hilarious article on grant writing!
The PI Blog
This blog exists because my wife seemed a bit tired of being the only recipient of my random pontifications on life and Science for many years; and gently encouraged me to vent in a blog instead. From time to time, I put down thoughts that occur to me as I naiively stumble through a life in Science - bestowed upon me by accident (literally!). Please keep in mind that these musings are rather obvious things of little or no use to anyone, and are certainly not personally targeted in any way, even though they are obviously derived from my experiences. OK, enough said.