Mobile advertising platforms and others waiting for the space to finally lift off can take comfort from the latest Mobile Advertising Report from Nielsen Mobile and its finding that about 23% of U.S. mobile users–about 58 million people– report receiving an ad over their cell phones within the last month.

Even more importantly, half of those (51%, or about 28 million) report acting on that ad in some way. The most popular response to a mobile ad was sending at least one SMS message; 26% of those reached by an ad did that. Nine percent said they responded to the solicitation by using “click-to-call”, a feature that lets them dial a phone number contained in an ad with a single button push.