This is on almost every guide to riding a bike safely:
On Kickstarter, Nicholas Fjellberg Swerdlowe has designed a set of plastic hooks that are designed to do do exactly that, to enable you to hang groceries from the end of your handlebars. He writes:
DO NOT hang grocery bags or carry loose loads on your handlebars as they can upset the control of your bicycle and prevent you from properly turning your front wheel to avoid a crash.
The Bag Buddy snaps on to your bicycle grips and serves as a clamp, using the weight of each bag to tighten its hold. Two tubular clamps secure the bag hooks mounted on either side of the body. While transporting groceries, the bag buddy rotates the angle of "bag swing" 90 degrees away from the bicycle; positioning the bags parallel to the frame and securing the groceries away from the front tire.
Isaac Newton would have a different opinion. He might point out that a 30 pound pendulum is going to keep going in the direction of travel while the wheel turns into it. It's called momentum. you can't "rotate the angle of bag swing" in this universe. You don't want to put a 30 pound pendulum at the end of your handlebars.
Scott Spitz of Urban Velo calls the Bag buddy THE WORST BICYCLE ACCESSORY EVER, in upper case yet. That may be harsh, but there are lots of inexpensive and safer alternatives, like panniers (here's a design you can make for four bucks) and baskets.
In Toronto, a cyclist was killed this summer while carrying groceries on his handlebars; he lost his balance when he hit some streetcar tracks.
While TreeHugger loves good design and loves bikes, this is one idea that should stay on the drawing board. It is more suitable for a Darwin Award than for Kickstarter Funding.