Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Millennial Media (UNKNOWN:MM.DL) plummeted more than 24% during intraday trading Wednesday after the company not only released quarterly results, but also took the opportunity to announce a significant acquisition.

So what: Quarterly revenue increased 45% year over year to $57 million, while the company's GAAP net loss worsened to $3.1 million, or ($0.04) per share, as compared to a GAAP loss of $0.03 during the same year-ago period on the same basis. On an adjusted basis, however, net income came in at $0.02 per share, compared with $0.01 per share adjusted loss this time in 2012. While revenue missed expectations, adjusted earnings actually beat estimates, which called for a loss of $0.01.

Millennial Media also said in a separate press release it has signed an agreement to acquire privately held mobile advertising specialist Jumptap in a "predominantly stock transaction." Specifically, when the transaction closes, Jumptap shareholders will receive around 24.6 million shares of Millennial Media stock, amounting to 22.5% pro forma ownership.

Now what: The revenue miss and added risk from the acquisition was enough to prompt downgrades Wednesday from at least two analysts. What's more, as fellow Fool Rick Munarriz pointed out already, Millennial Media's worrisome pro forma guidance of combined growth between 40% and 44% suggests one of the two companies' growth rates aren't stacking up. Given that, and also considering there are plenty of other less-risky investment options out there, I can't help but think the market got this one right.