I recently spent a night in a hotel and was surprised to find a $1.50 "safe fee" on my bill. Yes, the room had a safe in it. But I hadn't asked for one and hadn't used it. The charge was removed from the bill upon request. That was a helpful reminder that we should all pay attention to fees.

Consider your friendly neighborhood bank. According to a survey by the nice folks at the Consumer Federation of America, all of the largest banks they surveyed, including Fifth Third Bank (NASDAQ:FITB) and SunTrust (NYSE:STI), pay overdrafts at their own discretion and charge overdraft fees without first contacting customers. Worse, these fees have been rising. According to the survey, Bank of America (NYSE:BAC), for example, charges $35 per overdraft above $5, and additional "sustained overdraft" fees if the overdraft isn't resolved within a few days.

Airlines, meanwhile, are charging more for excess baggage and when you want to change your reservation.

Another important set of fees to consider are those levied by mutual funds. Never forget how influential those can be. If two funds average a 12% return over 20 years, with one charging an annual fee of 1% and the other charging 2%, they will grow a $10,000 investment to $80,600 and $67,300, respectively. That's a difference of $13,300 -- which isn't chicken feed.

You can match the market's return easily and inexpensively via an index fund -- some of which charge 0.10% or less per year. An S&P 500 index fund will instantly have you in 500 big American companies, such as Boeing (NYSE:BA) and Hewlett-Packard (NYSE:HPQ). Also, as a fund grows bigger, look for its fees to fall -- and if they don't, that's a red flag.

The silver lining
While the proliferation of fees can hurt us as consumers, perhaps as investors we might take some comfort in them. After all, what seems sneaky and insidious to our consumer side may strike our investor side as innovative, resourceful, and ultimately profitable. Hotel companies such as Marriott (NYSE:MAR) and Starwood Hotels (NYSE:HOT) could stand to gain from such fees. If a hotel company averages 100,000 rooms booked per day and charges $1.50 for safes, it would amount to $150,000 per day and nearly $55 million per year.

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Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article. Try any of our investing newsletters free for 30 days. The Motley Fool is Fools writing for Fools.