(Business 2.0) – 1. PODCASTING

Yes, it's nice to get MP3s downloaded to your iPod. But where are the revenues? Podcasting will continue, but as a business, it's the latest iteration of CB radio.

2. SPACE TOURISM

Travel to the final frontier is riskier than buying a vacation home in Aspen. When the first billionaire perishes in the icy void of space, it'll take years for this nascent industry to bounce back.

3. OUTSOURCING

It works for rote or clerical tasks, but creative and management functions are still most effective close to home. If your job hasn't been outsourced by now, it's unlikely to happen in the years ahead.

4. DOWNTOWN CONDOS

In cities like Chicago, Miami, and San Diego, short-term speculators snapped up many of these "entry-level" homes. With price-to-rent ratios at absurd highs, it's time to head for the exits.

5. CHINA RULES THE WORLD

Don't forget your recent history: Japan didn't surpass the U.S. economy in the 1980s, and it's unlikely that China will in the next half-century.

6. HIGH-DEFINITION DVDS

Which will it be: HD-DVD or the incompatible Blu-Ray format? Get ready for a rerun of VHS vs. Betamax--if, that is, consumers want high-definition DVDs at all.

7. HYDROGEN-POWERED VEHICLES

The technical challenges are huge, and they will probably take 10 to 15 years to overcome. Until then, you can safely ignore hydrogen hype.

8. PRIVATE-LABEL MOBILE-PHONE SERVICES

Lucrative niches are few and far between, and the best ones (such as teens or sports fans) are already taken. Whatever's left is likely to be too small or too hard to reach to turn a substantial profit.

9. CELEBRITY CLOTHING BRANDS

Sean "Diddy" Combs made celeb-branded clothing fashionable. Beyoncé, Jennifer Lopez, and Gwen Stefani followed. Now comes proof that this fad will fade: Jessica Simpson has launched her own line of plus-size jeans.