The Samsung Instinct beat out the iPhone in the number of ad impressions last month on Millennial Media's mobile ad network.

Millennial Media recently released the results from May's U.S. Scorecard for Mobile Advertising Reach and Targeting, or SMART report, showing that the overall reach of the mobile Web has increased to 59 million nationwide, and that the mobile ad network now reaches more than 73 percent of the U.S mobile Web. The scorecard also showed that paying attention to focused demographic targeting led to overall lower costs to engage mobile users.

"The growth of the mobile Web can be attributed to several major market trends," said Mack McKelvey, vice president of marketing at Millennial Media, Baltimore, MD.

"There is a combination of more mobile users overall and increased page views per user and also a greater processing power, screen size and network speed of devices which is delivering a much-improved mobile Web experience," she said.

Some other market trends that have shifted mobile Web usage are the all-you-can-eat data pricing, auto-provisioning from carriers and the increased availability and quality of content that is specifically created for mobile browsing.

Finally, demographics are shifting around the increasing adoption of the iPhone and other smartphones across the socio-economic spectrum, leading to staggering mobile Web usage.

SMART reported that more retailers have taken advantage of mobile as a well-worthy channel to deliver direct response tools.

Also, SMART reported that the Instinct from Sprint replaced the iPhone as No. 1 on Millennial Media's list of Top 20 mobile phones in May.

"Sprint has had aggressive marketing promotions around the Instinct " for example, the featured videos of one-on-one Instinct versus iPhone 3G ?battles,' and they remain a leader in the mobile data market," Ms. McKelvey said.

"They were the leader with all-you-can-eat data pricing, and this continues to benefit their market perception," she said.

Samsung and Apple have been battling over the No. 1 spot for a while. However, Motorola beat out LG for the No. 3 spot as device manufacturer on the Millennial Media Network.

A highlight of May's edition of SMART were results from Memorial Day.

The scorecard showed that travelers who were away from their computer relied, in the majority, on the mobile Web for information on travel and buying decisions during the Memorial Day weekend.

"This is the first time that Millennial Media has specifically looked at interaction rates during a holiday weekend in comparison to the month overall, but a preliminary review of the data and the results from Memorial Day would support this," Ms. McKelvey said.

SMART showed that Wi-Fi use over the holiday dropped 10 percent, which is a great representation of the "substitution effect."

This drop was not in accordance with other weekends in May. But due to the travelers who stopped using Wi-Fi, total network usage went up 11 percent.

Millennial Media also saw a 12 percent lift in interaction rates over the holiday weekend.

"Our recently added publishers have significant reach impact," Ms. McKelvey said. "We have 11 of the top 25 now in our network, as well as many more in the Nielsen Top 100.

"We will continue to be focused on extending our reach in order to create the most impactful audiences for advertisers," she said.