Summing up what's being said in the comments, the two main points are: 1. Subjective: are you really really willing to spend a lot of time and energy (not to m

Summing up what's being said in the comments, the two main points are: 1. Subjective: are you really really willing to spend a lot of time and energy (not to mention money) on the idea, to the point that it becomes the only subject of your thoughts? (Paul Graham wrote two inspiring pieces on this: http://paulgraham.com/top.html http://paulgraham.com/top.html and http://paulgraham.com/determination.html http://paulgraham.com/determination.html) 2. Objective: is there really a market, is people really willing to pay for your solution? etc... There was a submission a while ago on HN about a technique dubbed "Ghetto Testing" that was quite interesting: http://news.ycombinator.com/item?id=1485057 http://news.ycombinator.com/item?id=1485057