A few days ago I was placing an order online for an item indicated as "in stock, ready to ship." In the 60 seconds it took me to add it to the cart and initiate checkout, the item came up as "out of stock" with an estimated ship date 2 weeks out. I did not order.
I have also had instances where items have changed price in the cart, and my decision to order is based on how much of a difference in price and/or how bad I really want the item. If the item only changes by a few dollars I usually go ahead and order.
I work in an industry where prices on items can change a few times a day so it does not surprise me all that much to see prices change in an online cart. We do our best to honor previous price quotes in all instances of a price change, however sometimes it just isn't possible.