Making money on other people's obsessions isn't a new idea. But filling an ETF with companies that indulge in so-called "sinful" pursuits is.

The FocusShares ISE SINdex Fund (NYSE:PUF) is the first ETF to give investors an opportunity to concentrate on the sin industries. These companies include casinos, alcohol producers, and cigarette manufacturers.

Cashing in on sin
Sin can be profitable, since companies which provide the goods and services related to gaming, alcohol, and tobacco have a somewhat captive audience -- and in some situations, an addicted consumer. With such a committed base of customers, these industries are unlikely to fade away soon and tend to hold up fairly well in economic recessions.

The fund tracks the ISE SINdex, which includes 30 companies in the sin industries. Top companies in the index include gaming machine-maker Bally Technologies (NYSE:BYI), tobacco and alcohol producer UST (NYSE:UST), and well-known beer brewer Molson Coors (NYSE:TAP).

Sin isn't for everyone
Even if you find the sin industries morally repugnant, the SINdex Fund may be useful -- for one thing, it makes it easy to bet against those industries by selling shares of the ETF short. Its expense ratio of 0.60% makes the fund somewhat expensive, but not sinfully so.

Human nature being what it is, the products and services provided by the sin industries are likely to be in demand for the foreseeable future. However, the fund is obviously highly susceptible to any single economic, market, or political event affecting these industries. Government has a heavy involvement in the regulation and taxation of these industries, and there are numerous litigation issues which can impact the companies involved. With such a narrow focus, this fund is certainly not for everyone, and even those investors who are willing to give it a try shouldn't bet the farm on this one.

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Fool contributor Zoe Van Schyndel lives in Miami and enjoys the sunshine and variety of the Magic City. She does not own any of the funds or securities mentioned in this article. The Motley Fool has a disclosure policy