(FORTUNE Magazine) – The numbers are in. During the fourth quarter of 2000, the proportion of the U.S. adult population that uses the Internet shot well past the 50% mark, according to the Pew Internet & American Life Project. While that doesn't necessarily mean that half of our grandparents are acronym-spouting Webheads, it is a significant milestone in the diaspora of the Internet.

But those numbers mask something that has only slowly become clear and that's potentially more significant: After the first blush of enthusiasm burns off, the Web can become a frustrating and bottomless time sink. Worse, it can be rather boring. Sure, you can buy movie tickets online, check your portfolio, exchange e-mail with friends and business associates or chat with anonymous acquaintances, download music, share photos, shop for just about anything, watch the news, and all that. But when it comes down to it, most of us don't have the time, patience, or, yes, bandwidth to plumb the infinite possibilities of the Web. Instead, we limit ourselves to a modest routine of familiar sites and tasks that support our everyday lives.

It may sound arcane, but this phenomenon actually goes a long way in explaining three disconcerting business trends: the collapse of dot-com e-commerce, the drying up of online advertising, and even the flattened growth in sales of consumer PCs.

The first is pretty obvious. E-commerce promised instant gratification but in reality delivered only a watered-down "virtual" version. While you could indeed buy something in a New York second, you still had to wait for the physical infrastructure to deliver what you bought (except for software and content). That's fine for a book or a CD, but it's no substitute for stopping by the bakery on the way home to pick up a still-hot French baguette. And sellers of high-ticket, high-tactile items like furniture or fine clothing have learned that customers can't shake the urge to touch and see items before they buy.

As for the decline in online advertising, well, as Web users narrow down the number of sites they visit, they also focus on what each site will do for them and are less willing to travel where its attendant ads might lead. Click-through rates stink at even the busiest sites--everyone's so focused they don't even notice the banner ads, however well targeted.

The link between online ennui and the sluggishness of the consumer PC market is a little more subtle. It boils down to the fact that buying a better PC won't necessarily improve your online experience. Bandwidth is a much bigger constraint on performance, making a cable modem or DSL a much better investment.

What can reignite users' enthusiasm? Most pundits point to smart cell phones and other wireless devices. But those devices can only provide services for tiny screens or clunky voice-recognition technologies. Anyone who has used these services can tell you that they are as frustrating as they are useful. Yes, they'll improve, but there are finite limitations.

The Internet will get better, eventually. Websites will learn to work in concert to provide customized services that also take more advantage of the computing power of your PC, and they will work to get you what you need even when you're not logged on. Microsoft and Sun and a host of other companies are hell-bent on making that happen, but it's a hugely complex challenge, one years away from fruition. So if you're eagerly looking forward to the next truly exciting phase of the Internet, there's just one phrase that's appropriate, one familiar to anyone who has tried to check out a busy Website recently: Hurry up and wait.

--Brent Schlender