There would have to be a company that handled the exchange. Then Newegg could just display the current BTC cost (based on the company's api). When people pay using BTC, it works just like paypal. They go to that companies site, pay, then they notify Newegg the person has paid and to proceed. Then the company pays Newegg the USD equivalent.
On Neweggs side, they're still selling it for USD, nothing really changes. The bonus is no chargebacks.
The bitcoin company handles selling the bitcoins, covering their costs, and provides the API/setup for any business to sell in BTC and get paid in USD. I'm not sure how much profit there is going to be, this is probably a business that loses money in exchange for legitimizing bitcoin and gaining consumer and business confidence. If I was that guy with 250k bitcoins I'd no question use 10k of them to fund this business in order to protect my other 240k coins.
No real business is going to screw around with converting/accept bitcoins. There has to be a specialized bitcoin company that will accept the incoming bitcoins and then turn around and pay the online retailer in USD. Just the fact there's no charge backs should be at least some incentive.
It's like saying you want Newegg to accept gold bullion. Newegg isn't going to screw around collecting gold bullion anymore then they would bitcoins. But if another company would handle accepting/exchanging it to USD, then it makes a lot more sense.