Captain Kawaii

Whenever you are approached for a job and the potential client discusses what they want to do...and you know its a fail as they outline it...do you tell them its sure to be a fail, suggest additional small amounts of work or do you just sign em up and give em what they want?

For example, they say they want to do A+B and then go to market.

However, you know from the market, from experience etc that A+B+C is required or the client will be unhappy with the results.

2 cents anyone?