Mobile ad network Millennial Media on Wednesday reported revenue increased 75% in the second quarter, with a growing base of advertisers and app developers using its platform.  The company posted a net loss of of $2.2 million, or 3 cents per share, compared to a loss of $152,000, or 9 cents a share, for the year-earlier period. The second quarter marked a narrowing loss from the $4 million, or 5 cents a share, from the prior quarter. Revenue rose to $39 million from $22 million a year ago, and from $33 million in the first quarter. The growth rate of 76% was also up from 53% in the first quarter. Analysts on average had expected Millennial Media to report a loss of 5 cents a share on revenue of $38 million. After going…