We make all sorts of purchases from smaller merchants because we know they can't just take the money and run when we pay via credit card. I do it all the time. That way I don't have to just buy from Overstock.com or Amazon.com, but all kinds of merchants. I don't have to implicitly trust that a merchant will deliver the goods to me on time and in the fashion they say they will. I know they will or I can initiate a chargeback. And as far as "Presumably Overstock.com is a reputable company, and they would honor their guarantees"... I don't have to presume anything. I know I can get my money back if they fail to deliver.
I had to do this recently with a site that I expected would be reliable. One that I'd enjoyed the free services of for the past 5 years and had no problem placing a $40 order to download some premium content from. They never bothered to deliver it and wouldn't respond to email, voicemail or twitter. So, I initiated a dispute via PayPal and got my money back. If I'd paid with bitcoin, I couldn't get my money back.
I run my own small business, have worked with many other small businesses, and have friends running all kinds of other small businesses. I don't know of ANY legitimate business that "cannot take credit card purchases because of possible chargebacks".