As writer William Goldman famously said of Hollywood, "Nobody knows anything". And to a certain extent it's the same in the world of venture capital (VC). Just as studio executives never know how well a movie will do until it opens, so venture capitalists can't be sure which of their technology investments is the one with the mystery ingredient that will guarantee the big pay-off.

After all, who would have predicted that Microsoft would invest its millions in a social networking site that—among other things—allows members to throw sheep at each other? But that's what happened last year at Facebook.

VCs certainly dug deep last year, with investment by US venture capitalists hitting a high not seen since the heady days of the dotcom boom. And yet the outlook for 2008 is less certain, with the British Private Equity and Venture Capital Association recently warning the clouds are gathering and that this will not be an easy year for the economy or for private equity.

Still, don't weep for the money men too soon. There are still plenty out there with their riches burning a hole in their pockets, even if, as a result of the credit crunch, they might not be able to raise funds as cheaply as they did a few years back.

So what will they be spending that money on?
The social networking frenzy that sent Facebook rocketing last year is likely to continue, and there will be a host of contenders trying to steal its crown. But there will also be plenty of room for companies that figure out how to actually make money out of social networking rather than simply racking up huge numbers of users.

Interest may also shift away from the consumer social networks to those set up for businesses, and we may see another surge in interest in virtual worlds, especially if they can be combined with the mainstream social networks.

And while many may have thought the dotcom boom was over long ago, venture capitalists would seem to disagree. Start-ups with business models that depend fundamentally on the internet infrastructure attracted billions in investment last year—and that's unlikely to come to a halt.

Clean and green technology has been a popular investment for a few years now. And with both government and consumers putting pressure on businesses to buff up their green credentials, strong demand for technology-based innovation will continue.

This means technologies that allow companies to reduce their carbon footprint (perhaps by reducing the need for air travel) and monitor and reduce their power consumption (by making hardware or data centres more efficient) may prove popular investments.

Also, if the credit crunch continues to squeeze companies, one thing end users may cut back on is investment in IT hardware. So anything that allows them to squeeze more use out of what they have—such as virtualisation technology—will be of interest.

Mobile is another sector with huge potential for growth, according to Peter Rowell, chairman of investment bank Regents Associates, particularly mobile internet and innovative ways of capturing payments.

Mobile content aggregation and delivery—where there is still no clear leader—is another area that may attract investors. Applications offering location-based services are likely to be another hit, and the area of smart medical devices is still seeing growth.

Of course, as happened last year, the big success of 2008 is going to come out of nowhere—don't forget, nobody knows anything. And even if someone does know what it will be, they certainly won't be telling. Yet.

Steve Ranger is the editor of business and technology website silicon.com