When 7% of a retailer’s unique monthly visitors are on iPads, it’s a safe bet it’s time for an iPad app. That’s why Overstock.com Inc., also known as O.co, has today released an iPad app that gives consumers using the mega-popular tablets access to the e-retailer’s complete inventory of products in a fashion optimized to fit the iPad’s 9.7-inch screen and make use of the touchscreen style of tablet computing.

The app enables Overstock.com customers to search, browse and purchase products. It opens with a splash of imagery, five rotating hero shots atop the home screen. Below are popular categories, each section divided into squares showcasing four products. Categories include Top Sellers, Furniture, Bedding and Jewelry. A bar on the home screen includes buttons to navigate by all product categories, search all products and sign in to an O.co account.

Two key features of the app are “infinite scrolling” and social sharing, says Sam Peterson, senior vice president of marketing at Overstock.com. Infinite scrolling is a term used by tablet site and app developers to describe the feature that enables a shopper to swipe down on the screen and continue to see product after product without the need to refresh the screen. That’s different from e-commerce sites, which present search results divided into pages, requiring a shopper to click to a new page for more results.

The app, built in-house, also lets customers share products via integrated links to Facebook and Twitter. Many studies have shown that mobile consumers are very social, often accessing social media sites and apps from their smartphones and tablets.

The O.co iPad app comes at the start of the 2011 holiday shopping season, and the e-retailer says the app will help iPad customers shop in a way designed specifically for them.

“We’ve simplified the gift-giving season by developing a simple yet elegant interface that will help the Overstock.com customer easily search, compare and purchase their favorite products,” Peterson says. “Our new O.co iPad app lets customers find great deals on lots of products from the convenience of their iPad and allows customers to easily share great deals they find with their friends through Facebook and Twitter.”

Overstock.com, which also offers an m-commerce site and iPhone app, is No. 22 in the Internet Retailer Mobile Commerce Top 300. The retailer reports that the number of unique monthly visitors shopping on iPads is one million. The Internet Retailer Top 500 Guide estimates Overstock.com’s total unique monthly visitors to be 15.3 million. Overstock.com is No. 27 in the Top 500.