Historically, tumultuous times offer some of the best opportunities to buy stocks, and the market's recent mess surely qualifies. Despite a global push toward alternative energy, many investors think oil and funds that track it, like United States Oil (NYSE:USO), remain a solid investment.

In our Motley Fool CAPS community, nearly 86% of the 1,279 investors rating the exchange-traded fund (ETF) are bullish, so there's no shortage of reasons why United States Oil will thrive, three of which I've highlighted below.

But here at The Motley Fool, we're all for looking at both the good and bad sides of an investment. Once you're done with this article, you can read the case against United States Oil, weigh in with your own comments below, or rate United States Oil yourself in CAPS.

1. Weak dollar
The price of oil and the U.S. dollar tend to have an inverse correlation that is only growing in strength. As the dollar has showed continued weakness lately, commodities like oil and gold have strengthened, benefiting investors in United States Oil and gold producers like Yamana Gold (NYSE:AUY). Many investors predict a further weakening dollar as the U.S. government piles on debt, and there has been more discussion of the dollar taking a lesser role in world trade.

2. Strengthening economy
Some investors and analysts think that the worst of the recession is behind us and believe that oil will benefit from higher energy consumption. The global downturn hit demand for travel aboard airlines such as UAL's United Airlines (NASDAQ:UAUA), but the airline and some other key companies see business coming back.

3. Scarce resource
Many oil bulls argue that we'll eventually reach "peak oil," when we've hit the peak of global oil production. Despite large oil finds by Petrobras (NYSE:PBR) and ongoing exploration by others, there's a finite amount of oil that can be pulled from the ground by producers like Chevron (NYSE:CVX) and ExxonMobil (NYSE:XOM). Many investors have a positive outlook for long-term oil prices -- even Warren Buffet after his ill-timed purchase of ConocoPhillips (NYSE:COP).   

To see details of what CAPS members are saying now about United States Oil, just click on over to Motley Fool CAPS and have a look -- or add your own thoughts directly to this story in the comments box below. And don't forget the summary of the bearish argument.

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Fool contributor Dave Mock has three reasons why lima beans shouldn't be part of his meals. He owns shares of ExxonMobil. Petrobras is a Motley Fool Income Investor recommendation. The Fool's disclosure policy would lay down its coat for any fair maiden.