According to a number of analysts, the cumulative mobile advertising revenues in Europe's five largest economies (France, Germany, Italy, Spain and the U.K.) will top $1 billion in 2015. On its way to this, as a new whitepaper from mobile ad optimization and advertising firm Smaato points out, Europe faces a number of unique challenges. As the report's author, mobileSQUARED's chief analyst Nick Lane notes, the upcoming 2012 London Olympics will be a catalyst for driving total mobile advertising revenues in these countries beyond the $1 billion mark.

Currently, mobile advertising campaigns in Europe tend to be relatively small. According to mobileSQUARED, advertisers in the U.K. tend to spend around $15,000 to $20,000 per campaign, and in France, Germany, Spain and Italy, these numbers tend to be even lower (between $10,000 and $15,000). In the U.S., on the other hand, the average campaign spend is now closer to $100,000.

As the number of mobile users in these countries growths in the next few years (from 65 million by the end of this year to - according to some estimates - 160 million in 2015), the mobile advertising industry will obviously continue to grow as well. While mobile Internet usage is dominated by social networking today, Lane thinks that the percentage of social networking traffic will fall over the next few years, "as users vary their browsing experience as their understanding of the mobile Internet increases."

From the report:

Up to 2012, mobile advertising revenue growth will experience a steady increase, but spend will greatly intensify as advertisers look to capitalize on the global appeal of the Olympics.

Lane estimates that a majority of the increased spending will come from banner ads, but also from publishers who will try to monetize their growing mobile traffic. He also assumes that the arrival of more geotargeted advertising solutions will generate premium returns for publishers.

The main catalyst for mobile advertising growth in Europe in the next few years will likely be the 2012 London Olympics. While less than 3% of brands are currently active on mobile, this should change considerably over the next two years, as these advertisers gear up for the Olympics. By 2012, Europe's five largest economies will already have more than 100 million mobile users and Smaato expects that the investments of Europe's largest brands will "fuel revenue growth over the forecast period."

Bonus: As we are heading to 2012, Smaato's latest statistics show that are are still some differences between the U.S. advertising market and its European counterpart. In the U.S., for example, Windows Phone users leading the pack with regards to click-through rates, followed by Apple users, while in Europe, BlackBerry users are more likely to click on ads (also followed by iPhone users). In terms of fill rates, Europe is lagging slightly behind the U.S., though the numbers are growing in both markets.