As the summer months draw to a close, many ETFs find themselves in negative territory on the year; an extension of 2009's magnificent rally has simply not materialized. Many of the disappointing performances from equity ETFs have been easy enough to explain, as scenarios that have played out countless times before have dragged down stocks. The iShares MSCI Spain Index (NYSE: EWP), for example, has been pummeled by sky-high unemployment, an impossible budget situation, and the prospect of a a prolonged period of negligible real economic growth. Against that backdrop, it is not surprising that EWP has lost about 15% in 2010.

Other ETFs, however, have simply run into some tough luck; events or relationships that few could have foreseen have dragged many popular funds lower in 2010. As another Friday the 13th rolls around, we profile a few ETFs that have experienced more than their fair share of bad luck this year [for more ETF insights, sign up for our free ETF newsletter]:

iShares S&P Global Clean Energy Index Fund (Nasdaq: ICLN)
To many, an investment in alternative energy seemed like a surefire winner at the beginning of the year. As the U.S. and other industrialized nations go on and on about the importance of ending dependence on foreign oil, the temptation to invest in industries that could potentially solve the energy puzzle is understandable.

Halfway through August, the outlook for clean energy still looks bright, especially after the Obama administration recently attempted to jump-start its promise to develop alternatives to fossil fuels. Yet ETFs focusing on various corners of the clean energy market are among the worst performing equity ETFs of 2010; many have lost more than 20% of their value since the start of the year.

Strangely enough, the driver behind these disappointing results comes from across the pond; the dismal performance of ICLN and other clean-energy ETFs is at least partially attributable to a bit of bad luck. As cash-strapped governments across Europe have been forced to implement harsh austerity measures, many countries that once offered lucrative subsidies have drastically scaled back financial support for still nascent clean energy firms (some have eliminated subsidies altogether). That has dimmed the financial outlook for alternative energy considerably, despite the fact that interest in the sector remains high [see Complete Guide To Clean Energy ETFs].

That development has weighed heavily on a number of clean energy ETFs, including solar (TAN, KWT), wind (FAN), and diversified funds such as ICLN; all are down sharply on the year. You might not have expected that one of the biggest losers from Europe's lingering fiscal crisis would be alternative energy; ICLN's rough 2010 should serve as a nice reminder of the risk that comes along with any ETF investment.

Oil Services HOLDRS (AMEX: OIH)
Perhaps the biggest story of the year took place off the coast of Louisiana, though the repercussions will be felt around the world. The leaking oil well in the Gulf of Mexico has now been plugged, but the fallout from one of the worst environmental disasters in U.S. history will continue for the foreseeable future. The Deepwater Horizon oil spill has battered shares of BP (NYSE: BP) this year, as the company has spent billions in cleanup efforts and set aside billions more to fund future liabilities that arise from the disaster.

But the British oil giant certainly isn't the only casualty. The Oil Services HOLDRS doesn't maintain any exposure to BP, but this fund is still down about 15% on the year. That's primarily because of the uncertain regulatory that now surrounds the oil services industry. The battle over the legality of a ban on deepwater drilling is ongoing, but even a repeal doesn't clear OIH's path for a rebound. With images of tar balls still fresh in the public's mind, Washington is unlikely to do any favors for Big Oil any time soon.

OIH has emerged as one of the biggest losers from the Gulf oil spill, paying for the transgressions of a firm that isn't included among its holdings [see Five Facts About HOLDRS Every Investor Should Know].

Claymore /NYSE Arca Airline ETF (NYSE: FAA)
It may seem strange to include FAA among the unlucky ETFs of 2010 considering that the fund has been one of the top performing equity ETFs; it is currently up more than 10% year-to-date. But those gains could have been even more substantial if not for the bizarre events that unfolded above Iceland this spring.

When the Eyjafjallajokull volcano erupted this spring, few could have imagined the havoc it would wreak on international travelers. As a giant ash cloud formed above the volcano, airlines were forced to cancel dozens of flights due to concerns over the safety of flying through the cloud. Air traffic in and out of Europe slowed to a trickle; by some estimates the flight cancellations were causing the global airline industry $400 million in lost revenue each day.

By the time the skies finally reopened, the eruption had cost the industry $1.7 billion according to the International Air Transport Association. The unexpected event no doubt had a negative impact on FAA, which tracks an index made up of international passenger airline stocks.

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