Source: Comcast

Let's not beat around the bush -- everyday folks aren't huge fans of Comcast (NASDAQ:CMCSA). In fact, they hate the company. Earlier this year, held a March-madness type bracket to determine the worst company in America. Readers were allowed to vote an each match-up to determine who moved on. In the end, the winner (if that's what you'd call it) guessed it: Comcast.

Investors, however, know that Comcast has some crucial advantages that make it worth owning -- like being the sole provider of cable and Internet services in many geographic areas it operates. That kind of advantage allows the company to rake in healthy free cash flow every year -- and it gives some of that back in the form of dividends.

That has helped the company post a 150% return for investors in the last three years. But while that's good news for those who owned shares back then, today's shareholders want to know what the future looks like.

The most important metric for dividend investors
When it comes to dividends, no metric is more important than free cash flow. This is a measure of the total amount of cash a company puts in its pocket during the year, minus any capital expenditures. In Comcast's case, capital expenditures usually involve spending to strengthen its infrastructure for cable and Internet connectivity.

In the end, it is from free cash flow that dividends are paid. Over the past six years, here's the company's free cash flow situation has looked like.

There are a couple of important things to note from the graph above. First and foremost, Comcast's dividend is imminently safe. Currently, only 29% of free cash flow is being used to pay out its dividend. That means that even though dividends have increased by 140% since 2009, there's still a lot of room for growth.

The major bump in free cash flow in 2011 is associated with the company's purchase of NBC Universal. And even though it might look concerning to see a drop in free cash flow in 2013, it was largely a result of the company's investment in the X1 Platform, which aims to give customers a better TV and movie viewing experience.

But what about the company itself
Based on the complaints of terrible customer service, you'd think that Comcast's top and bottom line would be suffering, but that's simply not the case. Aided in part by the NBC Universal acquisition, net income has increased by 20% per year since 2009.

These are very strong results. But there are two threats to the company's dominance that investors need to be aware of.

With cable operators fighting for a way to survive in the era of streaming television, the company's efforts to acquire Time Warner Cable (UNKNOWN:TWC.DL) are key to its future. The combined entity would account for one-third of all pay-TV subscribers, and would give it more bargaining power to lower content costs from cable companies.

As it stands now, Comcast is losing cable subscribers at a steady pace. It plans to make up for that loss by eventually charging per data usage for its Internet service. That's important because it would make up for the lost revenue because streaming through Netflix or Hulu can quickly add to your data usage.

The passage of the merger would be considered a win for many shareholders.

The X factor -- and second threat to keep an eye on -- in all of this could be Google (NASDAQ:GOOG) (NASDAQ:GOOGL) and its ambitious plans to create fiber Internet networks in cities throughout the United States. Although Google's foray into Internet connectivity is still in its infancy -- present in only a few U.S. cities -- if the company's offerings were to gain a strong foothold, it would be a major problem for Comcast and its shareholders.

Currently trading for 16 times free cash flow and offering a 1.6% dividend yield, the stock looks fairly valued given the competitive threats that its facing. If you want to buy shares today, you need to carefully weigh how serious you consider the two threats mentioned above.