It’s official. Fred Wilson says mobile, not web, will be the next hotspot for growth.  

“Web is flattish,” Wilson, co-founder of Union Square Ventures and early investor in Twitter and Zynga, wrote in a recent blog post. "But mobile is growing like a weed."
While mobile has likely been on the mind of many entrepreneurs recently (ahem, Mark Zuckerberg), Wilson pointed out where he sees the most traction.

There is a significant shift going on this year, much more significant than we saw last year, from web to mobile. It is most noticeable in games, social networking, music, and news, but it is happening across the board and it presents both great opportunity and great challenges.

According to Wlison, the big challenges in mobile are user experience and monetization. Mobile, he wrote, rewards feature-lightness (think Foursquare) more than feature richness (he believes Facebook should break its monolithic web app into a bunch of smaller, mobile apps).  Mobile users prefer application-specific services.  
As for monetization, Wilson wrote that companies should move away from display advertising, which he argued doesn’t work as well on mobile as it does on the web.  However, he added that commerce could take off if companies integrate a one-click purchase experience or a freemium model.  

If you are going to operate a media model on mobile, look at Twitter's model for inspiration. The ads are the default content object (the tweet) and are delivered right in the primary user experience (the feed/timeline). It's not surprising that more than half of Twitter's ad revenue is coming from mobile.

Earlier this month, Wilson wrote that this mobile shift necessitates the need for an aggregated audience measurement service that would combine user data from both mobile and web.