A few weeks back I interviewed long-range forecaster Paul Saffo of the Institute for the Future. It was an enlightening experience -- I learned forecasting the future is possible, and you don't need a crystal ball to do the job.

In interviewing Mr. Saffo, I asked him to rate 10 different technology trends as buy, sell, or hold over the next decade. Let the countdown begin:

10. Satellite radio. Saffo says buy: "It's already established."

Fair enough. Incidentally, our analysts at Motley Fool Rule Breakers agree and recommended XM Satellite Radio (NASDAQ:XMSR) to subscribers.

9. Voice over Internet protocol (VoIP). Saffo says hold: "I would buy the service for sure... [But] Voice over IP is about creating a new mode of interpersonal communication that I think will grow out of instant messaging. Call it voice and video over IP. I am still waiting to see the company that comes up with a new, compelling model there."

Me, too.

8. On-demand software. Saffo says buy: "The trend is certainly happening, and I think Salesforce.com (NYSE:CRM) is a really good example. But, at the same time, there are also free versions of similar software available, so I'm a little unsure as to where I'd place the money."

I sympathize. After all, Google (NASDAQ:GOOG) could be eyeing the market, which makes forecasting a winner other than, well, Google difficult.

7. Space tourism. Saffo says hold, even though he confesses to booking a reservation to the moon on the now-defunct Pan Am. "I think the trend is a little further off than people realize. After all, this is a big move from something that was the province of government to now the province of entrepreneurial billionaires. The fact is the way we get people into space is just damned dangerous. There is no way around that."

Oh, come on, Paul. Let's light this candle!

6. Robot-controlled surgery. Saffo calls it a cautious buy, but wonders if more efficiently caring for the well is an even better bet. "Once you can have personal diagnostics and wearable diagnostics, it is a huge change in medicine. ... It is a big market, too. This is the crowd today that buys Polar wristwatches because they are avid cyclists or avid tri-athletes. ... These are [also the] people who post pictures of their workout profiles from their Polar software."

Seriously? Posting a workout profile? Maybe I'm just too sedentary to understand that one.

5. Renewable energy. Surprisingly, Saffo says hold: "Today we have an energy monoculture based on petroleum. ... That sounds dangerous and so everybody says, 'well, what replaces oil?' The answer should be: No one thing. We need a balanced energy equation where we use a mix of renewables and things that we are not going to be so happy with, such as nuclear and coal power."

That's hard for a renewables fan like me to swallow, but, for at least the next decade, it's probably true.

4. Smart medicines that target diseased cells. Saffo says hold: "You have got the FDA [Food and Drug Administration] and all of the regulatory authorities standing between the laboratory work and the ultimate patient, so my guess is our pets will probably get them before we get them. The regulatory hurdles are lower. Also, look for medical tourism because you will probably be able to get it abroad before you can get it in the United States."

3. A $1 trillion market cap for Google. Saffo says hold: "I could argue with equal passion for both of the outcomes -- that it does make one trillion and that it does not -- which, to me, says the cone of uncertainty is just too broad. There are times to know when not to make a forecast, and this is one of them."

Equally, there are times when passing on what appears to be a promising investment can be the single smartest thing you can do for your portfolio.

2. Subscription TV. Saffo says strong buy: "I was having lunch with a good friend in Singapore about three weeks ago and he has got the video iPod. As we were talking I realized he buys Desperate Housewives three different times. ... He gets it on his video iPod. He then also watches it on his laptop. And then he watches it on TV cable. Hollywood is getting three cash streams out of the guy. He is an extreme case, but you know, he is an indicator that the form factor matters. Being able to see things at different times matters, and I think we are going to see some real surprises here. ... You could say that I am completely fascinated by the notion of 'Cellywood' -- Hollywood brought to life on little cell screens."

Does this make anyone else wonder why TiVo (NASDAQ:TIVO) hasn't yet been bought by Google or Apple (NASDAQ:AAPL)?

1. Virtual economies. Saffo, a big fan of online multiplayer game The Second Life, says buy: "Most people don't realize that their savings accounts are already just clouds of electrons bouncing off of satellites or stored on computer disks. We are adding this whole new dimension on top of life. It really is quite remarkable, especially when you consider that the word 'cyberspace' was coined in a novel by Bill Gibson before all of this stuff happened, and yet the term really does elegantly apply to what is going on today."

On the lookout for what's next
Is any forecast perfect? No, of course not. Surely some of Mr. Saffo's predictions will be wrong. But many could be spot-on. And he had a lot more to say. To read our entire interview, click here to take a free trial to Rule Breakers.

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XM Satellite Radio is a Motley Fool Rule Breakers selection. TiVo is a Motley Fool Stock Advisor pick.

Fool contributor Tim Beyers plans to be well on his way to early retirement by 2016. How about you? Tim didn't own shares in any of the companies mentioned in this story at the time of publication. You can find out what else is in his portfolio by checking Tim's Fool profile. The Motley Fool has an ironclad disclosure policy.