Biggest Online Purchase

I recently asked my grandfather what the biggest online purchase he would make is, and he told me that he has already bought a car on Ebay, and could be willing to buy larger. So what is the problem with purchasing online?
Security is a big issue, with credit card numbers and identity being stolen everyday. Entire bank accounts can be drained and credit scores can be ruined. In the long run, I dont think these are the main problems people have with purchasing online.
I think its with getting the items you bought in the condition you thought they were in. My dad said that he would definately buy a car online, but only through a reputable dealer. He would never buy something so costly through Ebay. The question that scares off buyers is this: Will I get what I paid for, in the condition I paid for?
For myself, I have bought a $1000 Electric Keyboard online, and I would be willing to buy up to about $5,000. But like I said, only from some organization that I can trust.