I see things somewhat differently. Sales people have a responsibility to themselves and their company to try and predict sales for many good reasons. Mostly to help balance company assets (inventory) that drive customer service. Engaging sales people directly with an on line tool ensures their commitment to the numbers and publicly displays the results for all to see and grade them. For example if we treated development people like you suggest treating sales people then we would never get any project completion dates and product planning would go south. I have managed sales people for over 20 years and they like to take the path of least resistance (don't bother with forecasting) but frankly they have the same responsibility as the rest of us to commit to a task and then complete it. Their are some fine tools out there for collecting sales inputs such as Silvon's Stratum Viewer product when combined with the Stratum Forecast engine the solution provides a complete sales forecasting and planning solution