Since AT&T (NYSE:T) announced its agreement to purchase DirecTV (NYSE:DTV.DL) for $95 per share back in May, DirecTV shares have traded pretty steadily. Some investors may be looking at the share price around $87, and thinking they could hold the stock for six months or so until the buyout goes through and make an easy 8% on their investment.

But there's a reason DirecTV's shares only sit in the high $80s. It's because there's still risk involved with the company even with the agreement in place for shareholders to receive $95 in cash and stock per share. Here are three reasons DirecTV's stock could fall and a look at the likelihood of any of them happening.

The merger doesn't go through
The FCC stopped its unofficial 180-day review clock last month at day 76. The hold-up is a result of the media companies, who have a lot at stake in both the AT&T-DirecTV merger and the Comcast-Time Warner Cable agreement. They want to make sure that their carriage-fee contracts with the pay-TV providers don't end up in the hands of other pay-TV providers in the review process.

The concern is legitimate, as media companies would lose negotiating leverage if other pay-TV providers know how much the competition is paying. Still, it's unlikely the pause it's causing will affect the FCC's decision. Indeed, both AT&T and DirecTV believe the merger will still be approved.

If, for some unforeseen reason, the FCC (or Mexican regulatory board) rejects the merger agreement between AT&T and DirecTV, the share price of DirecTV could stumble. Again, this seems very unlikely.

The stock price shouldn't fall far, however. DirecTV is still operating well, growing revenue and earnings despite currency-exchange headwinds in its growing Latin American business and a stagnating pay-TV market in the U.S.

AT&T's stock price falls
Even if all goes as planned, and the merger goes through just fine, DirecTV investors might not get a full $95 in compensation. $66.50 of that $95 will come in the form of AT&T stock, but conditions apply.

DirecTV shareholders will receive 1.905 shares of AT&T stock if AT&T stock price is below $34.90 at closing and 1.724 AT&T shares if AT&T stock price is above $38.58 at closing. If AT&T stock price at closing is between $34.90 and $38.58, DIRECTV shareholders will receive a number of shares between 1.724 and 1.905, equal to $66.50 in value.

In other words, if AT&T is trading at a price lower than $34.90 the day the deal closes, DirecTV shareholders will receive less than $95 in compensation. Shares of AT&T are currently trading near the bottom of the collar.

AT&T is doing quite well in the pay-TV and high-speed Internet market, but its bread and butter is in voice services. The wireless market is becoming very competitive, with aggressive moves from T-Mobile and Sprint putting pressure on the established customer bases of AT&T and Verizon.

We're still about six months away from the deal closing, so it's possible AT&T's stock could take a hit if competition cuts into its profit growth.

DirecTV takes on more debt
As part of the agreement to buy out DirecTV, AT&T also agreed to take on the company's $19 billion in debt. If DirecTV needs to take on more debt for some reason, it makes the acquisition more expensive for AT&T. The result is a decline in AT&T's stock price, which is directly tied to DirecTV's stock price. Basically, it's the last thing DirecTV wants to do.

DirecTV's huge subscriber base in the U.S. makes taking on more debt extremely unlikely, since it generates a consistent cash flow for management to invest in new satellites and expanding into Latin America. In fact, Latin American operations are on pace to turn cash flow positive by the end of the year.

On the flip side, there's little incentive for DirecTV to pay down its debt considering AT&T's current price level is still well below the upper band of the collar.

No guarantees in the market
I point out the potential of these events to illustrate that there are no guarantees in the market. DirecTV is expected to close a deal in about six months for the equivalent of $95 per share, but there's still risk involved with an investment even more than 8% below the buyout price.

While I think it's unlikely that any of the above events will happen, they all could and could have a negative impact on DirecTV's share price.