(FORTUNE Magazine) – Billions of cell phones! That thought turns the knees of investors and analysts to jelly--and their brains to slush. Their cell phone fantasy goes something like this: Over the next few years people will buy billions of phones equipped for wireless data. Out of all this will arise a whole new Internet, with all kinds of new investment opportunities: new Netscapes, Amazons, and eBays--even Ciscos and Microsofts formed (literally) out of thin air and creating (many, many) billions of dollars of new wealth! It's the wireless Internet, after all, the next new big thing!

Gentle reader, do forgive me. I admit to having been virtually useless to you on this. I've flip-flopped a few times and felt jelliness in my own knees. I really wanted to believe in this wonderful new world. I even got excited about stock quotes on my phone. But like a spurned lover, I now know the truth--and it hurts. Here are the three reasons that the wireless Web as it's imagined today is nothing more than a seductive chimera.

Data does not belong on a telephone: Telephones are designed--quite well--for talking to other people. The keyboard taps out strings of numbers. The screen on newer phones displays those strings and other useful stuff such as names of people you call. Sure, you can display and read data on those screens--if you squint. Sure, you can create text messages on the keypad--if you have fingers the size of an infant and the manual dexterity of a court stenographer. But for most of us this is anything but a natural act.

In other words, why did we ever think that browsing the World Wide Web on a telephone would be useful? Phones were never made for such a purpose, and now, after many, many designers have given it a try, they're still not useful for that purpose.

I'm on my third StarTac, this time with Verizon's digital service, which, unlike my old Sprint PCS, works almost everywhere (even on the banks of Henry's Fork in Idaho). The phone has a wireless data browser, but I've never turned it on. And I don't miss it. I'm just thrilled to have a phone that works as a phone.

Personal is tough: In the six months that I used a Sprint wireless data phone, I did not get one piece of important info via phone that I didn't already have from another source. Oh, it was fun to see stock quotes anytime and anywhere, but I can get the same data on my laptop, and since I'm not trading stocks every minute of the day, that's fine. Did I buy lots of stuff via my phone, like books, airplane tickets, and, yes, stocks? Are you kidding?

Even when information comes in more natural forms, like a real voice, it's useless if it isn't truly personal. Some people love a company called Tellme Networks. It has a so-called voice browser: Call 800-555-TELL, and just by speaking you navigate easily to traffic, weather, movie, stock quotes, and other data delivered by recorded voice. Cool idea. Except the information isn't useful. It's not personal enough. For instance, the traffic report for Menlo Park, Calif. (where I happen to work), is really a generic report for the San Francisco Bay Area. Ditto for weather. Some features do look cool: You can ask Tellme for a restaurant pick, like Thai food in Menlo Park. Tellme lists a bunch of restaurants, and when you hear one you like, Tellme dials it so you can make a reservation. But I can't imagine that I ever will need or want this feature--why would I trust a voice browser over my friends?

The only information that I want on my cell phone is highly personalized. And that costs so much--somebody has to produce it, distribute it, and then synchronize it for millions of individuals--I'm betting we won't see anything useful on this front for years.

What's the killer wireless data app? E-mail. Instead of buying that God-awful Sprint phone, I should have bought a Blackberry from Research in Motion. One after another of my techie friends has bought this thing and become consumed with its utility and design (it fits neatly in your palm and has a surprisingly easy-to-use keyboard and a clear, albeit small, screen). Geoff Yang, my co-investor in TiVo, sat through the last board meeting doing e-mail on his new Blackberry under the table (where the CEO couldn't see it). This was doubly frustrating to me: I've always prided myself on getting the best toys before Geoff, plus I had made a big deal out of how much I liked my wireless data phone.

So I'll get a Blackberry, and crawl into the next TiVo meeting with my tail between my legs. But I've learned my lesson: E-mail is killer data. It is completely personalized: You only get it when someone sends it to you. And that makes it the testing ground for the utility of wireless devices. Phones stink for e-mail. So forget about the wireless Web riding on the cell phone boom.

Instead, the key to the wireless data business is the success of devices like Blackberry. Heck, if these devices take off, then maybe we can start dreaming big wireless dreams again--but this time those dreams won't include cell phones.

STEWART ALSOP is a partner with New Enterprise Associates, a venture capital firm. Except as noted, neither he nor his partnership has a financial interest in the companies mentioned. He can be reached at alsop_infotech@fortunemail.com. His column may be bookmarked online at www.fortune.com/technology/alsop.