i think this is a problem in every industry. the following has happened way too many times to count
salesman: woo-hoo, i made the sale
us: great, what do they want?
salesman: something that will <insert technology that doesn't exist anywhere except scifi movies>
us: yeah, um. that's not technically possible
sales: but... I told them you guys could have it done by next wednesday

no offense to any sales folks reading this, but you tend to mess things up for the people who actually do the work. better to let mechanics, engineers, designers, etc. talk to the client before anything is finalized