Non-follow-through-er
n. (var. non-follow-thru-er). Someone who does not "follow-through" with his or her words or promises. Typically an "idea" person so wrapped up in his/her ideas that s/he does not take the time to actually execute one. Also, someone who is "flakey."
My frustration with non-profit organizations is that they attract non-follow-through-er (s) who spend all day concocting ideas for change, and fractionally less time towards implementing those ideas.