What a sad image.

Picture a shopping cart, loaded with a 40-inch HD TV, a Blu-Ray player and the entire fourth season of Weeds, just left there unattended in the middle of Best Buy. Forever. No one knows who abandoned this feast of hi-fi entertainment or why.

This tragedy occurs all the time in the world of online commerce, and retailers are always looking for ways of reducing it.

And more and more of them are using the power of video.

A new eMarketer report titled “Video E-Commerce: Innovative Models Drive Sales” shows that online video use jumped 378% in 2009 over the previous year among the top 50 U.S. online retailers.

Though customer reviews are still king, according to the report, more and more big shops are finding that videos boost conversion rates, reduce product returns, build brand identity and keep those digital shopping carts zipping through the checkout lanes.

I’m not sure if Zappos was surveyed for the report, but the consistently awesome shoe seller produces tons of video and social content to build customer loyalty and move shoes. Here’s one of many hilarious videos from the Zappos TV blog.

Have you ever been on the fence about an online purchase and had your mind changed by a video?