Socially responsible investing (SRI) has been around for a while, but it really caught fire a few years ago -- so much so that it has arguably become mainstream. What isn't arguable is that it's an influential force, part of a larger trend that has pushed companies from McDonald's (NYSE:MCD) to Dell (NASDAQ:DELL) to reduce their ecological footprints and become better citizens.

Nowadays, companies that green up and engage with their communities tend to attract investors, enhancing shareholder value. That's great. I'm all in favor of less pollution and more community engagement, and no matter your politics, I bet you are, too.

But as an investor, whenever I see a big happy shiny mainstream trend, I get really curious about the opportunities on the other side of it, in the dark corners that nobody's watching.

Why? Because often, the dark side is where the money is.

When sin can be mighty fine
The types of companies that socially responsible investors avoid vary, but "sin stocks" -- companies that sell tobacco or opportunities to gamble, for instance -- are on most SRI types' no-buy lists. That's too bad for those investors, because some sin stocks can present fine opportunities for profits, especially during tough economic times.

While casino stocks like Las Vegas Sands (NYSE:LVS) and Wynn Resorts (NASDAQ:WYNN) have suffered during the dark days of the downturn -- unemployed folks tend to forgo weekends in Las Vegas, it seems, and both companies are making risky bets on big properties in Macau -- there are some promising opportunities among tobacco stocks.

Where there's smoke, there's often profit
As an ex-smoker myself, I've got some heavy qualms about investing in tobacco companies. I probably don't need to recite the arguments against tobacco for you. But I can't deny the appeal of these companies as by-the-numbers investments. Tobacco is a high-margin, low-variable-cost business, and the best-run tobacco companies often sport solid dividend yields and amazing returns on equity. Consider:

Stock

CAPS Rating (Out of 5)

Return on Equity

Dividend Yield

Philip Morris International (NYSE:PM)

*****

95.2%

4.8%

Reynolds American

****

15.8%

7.5%

Altria Group (NYSE:MO)

****

84.9%

7.4%

Lorillard (NYSE:LO)

****

252%

5.1%

Source: Motley Fool CAPS, as of Nov. 3.

These companies aren't likely to show massive growth. While tobacco use is growing in some corners of the globe and among certain populations, the World Health Organization believes that the very-long-term trend could well be one of decline. But absent a massive global government crackdown on smoking, those dividends are likely to be rock solid for years.

These aren't stocks that will make you rich overnight. But doing a little research and grabbing a couple for your long-term portfolio at current prices -- and reinvesting the dividends -- is likely to result in handsome gains, with a minimum of downside risk. It's an appealing opportunity.

We have to ask
But there's a big "but." Are investors in these companies supporting the expansion of global tobacco use by participating in the profits? Regardless of how you feel about the legality of tobacco use, there's little debate about its dangers. How willing are you to attach, say, your retirement hopes and dreams to the continued prevalence of smoking? And (maybe worse), to its growth, especially in the developing world?

Personally, I go back and forth on that one all the time. I can't deny that a company like Philip Morris International looks like an extremely appealing low-risk stock. With value pricing, solid management, and a good dividend, it's exactly my favorite type of investment.

And yet, I haven't been able to bring myself to buy. I'm not an anti-smoking crusader by any means, but there are a lot of other value-priced dividend opportunities out there right now. What do these tobacco companies offer investors that we can't get elsewhere? I don't have a good answer to that question. Do you?

Good companies with attractive prices and sustainable dividends are exactly what James Early and his team look for at our Motley Fool Income Investor service. If you'd like to see their best bets for new money now, help yourself to a 30-day trial, completely free of charge.

Fool contributor John Rosevear limits his smoking to the barbecue cooker these days. He has no position in the companies mentioned. Dell is a Motley Fool Inside Value pick and Philip Morris International is a Global Gains selection. Try any of our Foolish newsletters today, free for 30 days. The Motley Fool has a smokin' hot disclosure policy.