Blame it on Kim Kardashian.

Shares of Glu Mobile (NASDAQ:GLUU) have been immensely volatile in recent months. Since last February, the stock is down only about 9%, but those who bought in July may have lost as much as half of their investment.

Glu Mobile went on a prolonged run last summer, surging on the back of its hit mobile game, Kim Kardashian: Hollywood. Unfortunately for shareholders, the popularity proved short lived, and though the game made money, it fell short of heightened expectations.

Let's dig in on this cautionary tale for investors surrounding the dangers of investing in companies dependent on mobile games.

Endorsements only get you so far
With Kim Kardashian: Hollywood, Glu Mobile successfully brought an age-old tactic to the mobile gaming industry: celebrity endorsements. The larger video game industry has been no stranger to the phenomenon (hit franchises like Madden NFL and Tiger Woods PGA Tour have been sold on name recognition) but it took Glu Mobile and Kim Kardashian to bring it to the app store.

Initially, it appeared to be a savvy move. At its core, the game was far from revolutionary -- largely a copy of another Glu Mobile title, Stardom: Hollywood -- but Kardashian's name attracted attention and downloads. At its peak, it was one of the most downloaded apps on the iTunes app store, but its often shallow gameplay failed to hold the attention of players, and its popularity quickly waned. Today, it's nowhere to be found on Apple's app charts.

In October, Glu Mobile shares plunged after the company reported a quarter that fell below analyst expectations and offered weak guidance. The success of Kim Kardashian: Hollywood boosted Glu Mobile's sales by 270% on an annual basis, but that wasn't enough to satisfy the expectations set by the game during its brief heyday.

No "hits" for longtime shareholders
This bad news isn't stopping Glu Mobile, however. In fact, the company extended its deal with Kardashian for another two years. Ultimately, it may prove fruitful, but the public markets have not been kind to mobile gaming companies.

Although individual games have managed to capture the attention of millions -- and the industry as a whole has exploded in size -- none of the associated stocks have rewarded longtime shareholders.

Zynga has been an outright disaster: Since its public debut, shares are down more than 70%. King Digital hasn't been nearly as terrible, but has still lost almost one-third of its value since it began trading nearly one year ago. Like Glu Mobile's recent run, interest in both firms was predicated on the viral growth of a few titles -- for Zynga its Ville franchise; for King Digital, Candy Crush.

But unlike more established video game series -- Super Mario, Call of Duty, or Madden, for example -- the success of individual mobile titles has always been short-lived. Perhaps because they're free to play, mobile games attract a different sort of consumer -- one less interested, less committed, and more likely to jump ship when the next hit game comes along. 

Perhaps one day a company will break that trend and deliver a steady stream of hit mobile games one after another. But until that day comes, mobile game stocks belong only in the most speculative of portfolios.