Let's get one thing clear: Since the Fed lowered interest rates to 0% at the end of 2008, high-yielding securities have seen an across-the-board rise in bid prices.
For some, it appears the economy is continuing to get better, despite the lingering problems in the United States and around the world.
In fact, Jeffrey Lacker, President of the Richmond Federal Reserve, recently said that if it were up to him, he'd abolish the Fed's bond-buying program immediately.
Apparently, he thinks the economy doesn't need the Fed's help anymore.
But if Lacker is right and the Fed takes his advice, then interest rates are guaranteed to shoot back up again.
And that's problematic for dividend investors.
We know rising rates lead to bigger yields from safer investments.
Which, in turn, leaves all those riskier, high-yielding investments - ones that shareholders have piled into over the past five years - in a precarious situation.
But that also means they have a long way to fall.
Take a look at these three MLPs that stand to lose the most.
High Yields and Mixed Blessings
Plains All American Pipeline, L.P. (PAA) supplies crude oil to refineries in the Midwest and is a major player in the sector.
Armed with an impressive system of pipelines, storage assets and terminals that ship crude in from as far south as the Gulf of Mexico and as far north as Canada, PAA is primed for expansion.
The company already has plans to extend its reach to include the West Coast, as well as broadening its services by incorporating alternative refined products like natural gas liquids and liquefied petroleum gas.
Since 1999, PAA has been generating consistent cash flow - and sharing that cash flow with its shareholders through dividends.
And like most other MLPs, PAA not only delivered steady returns throughout the financial crisis, but also raised its dividends along the way - at least once a year since 2001 and consecutively for the past six quarters.
Plus, it sports a current yield of almost 4%.
But that's not necessarily good news.
You see, the stock has more than quintupled in value since 2008.
After bottoming out during the financial crisis, Plains All American shares have gone from less than $12 to more than $63 per share to date.
Which means that, even if the company continues to produce cash flow at the same or better degree, when interest rates shoot up, its share price could fall.
In Good Company
But this isn't a problem that PAA will shoulder alone.
It's a legitimate concern for other MLPs, as well as stocks in general.
Lower interest rates have prompted investors to chase yields - but when prices rise, yields decline.
PAA's competitors have seen a similar growth trend in stock prices over the past five years.
Sunoco Logistics Partners L.P. (SXL) has seen shares increase by more than six-fold, from less than $10 during the financial crisis to more than $63 today.
Shares for Magellan Midstream Partners, L.P. (MMP) have experienced a comparable jump from under $10 per share up to more than $52.
There's no debate - these are commendable gains. And all three companies still produce appealing yields - even in our current economic environment - with both SXL and MMP yielding 3.15%.
But by historical standards, yields like these are relatively low for MLPs, and that's a direct result of high share prices.
Bottom line: For all of PAA's excellent qualities, a potential rising interest could decrease the stock's value. And that's worrying.
If the Fed stops supporting the economy by buying bonds and keeping rates extra low, that drop could be drastic indeed.