It's been nearly two decades since e-commerce became a reality. With the pioneers of Amazon and eBay, the internet has changed how everyone does business--including the old brick and mortar stores as well. All in all, it's been a very good thing for pretty much everyone across the board, save the few dinosaurs that never learned how to adapt (and thus were most likely on their way out anyway.)
Strictly speaking, the phrase "Web 2.0" refers to a basket of various interface changes that occurred around the turn of the century--namely multimedia capabilities, social networking, and basically a place where users generate content instead of simply being passive recipients of the information. Still, the revolution in how commerce is conducted also occurred around this time as well, so I think it can be safely bundled in with the updated phrase.
Sadly, however, I've found that many of the old stalwart websites have failed in their initial objective of making the activity of shopping a different endeavor. While the details certainly have changed, there's been a notable decline in quality, insomuch that navigating some sites are just as bad as having to get in a vehicle and going to a crowded store used to be.
eBay appears to be the poster child for this sort of thing. Over ten years ago I bought my first item. It was exciting and thrilling and awesome: here I was, buying something from some stranger, and I never had to leave the house or deal with a big box store or anything. I don't recall what it was, but it went from someone's junk drawer to my mailbox in about a week. The only transaction costs were modest shipping charges and a reasonably slim percentage from the corporation that brought us together. It was a deal that worked out for everybody.
Buying something on eBay right now is a horrible, awful experience. They have added about twenty new steps to listing something, each of which is basically a way for you to throw an extra fifty cents in their pocket for putting flashy blinking icons next to your listing (and since everyone is buying them, it's an arms race where the only winner is the buy taking the money). Everything is skewed against the seller; the feedback system has been altered to incomprehensibility and policies basically let the buyer get away with everything. Fees have gone up and gotten much more complicated. While they don't force you to use PayPal, there are penalties for not doing so (either through deliberately making it more difficult or an outright fee); given that PayPal has its own set of horrible anti-consumer issues, it ties everything together. Finally, if you sell something, they inexplicably hold your money for something like ten days for no other reason than to (apparently) piss you off.
Granted, I understand some of these policies: it's to prevent fraud, which to be fair was getting pretty bad. Still, a lot of the policies appear to be blatant money-grabbing endeavors. While it's obviously their purpose to make money, they've made it so bad that a casual user (such as myself) ends up giving them no money because it's such a pain in the ass.
eBay, of course, isn't the only offender. Plenty of web sites that once held promises of cheap prices and smooth transactions eventually degenerate down into crass unusability.Meetup.com, for example, used to be a reasonably decent mechanism for organizing groups. I just went there after not being active for a few years and it's an absolute bloated mess. I can't make heads or tales of anything because the setup is so remarkably unintuitive as to be almost useless.
The main exception to all this is Amazon. While they aren't perfect, they've done a pretty good job of combining growth, ease of use, and profit margins where going there is a much better experience today than it was a decade ago.
There's a reason for a lot of this, of course. People had these grand ideas about how the internet would be completely different, only to get bogged down in the same details that plenty of normal business have been for centuries. The great internet crash of the late 1990's weeded a lot of these out, which is why Web 2.0 had such promise--they were going to learn from their mistakes and grow. Sadly, it increasingly seems like this is no longer the case.