NEW YORK ( TheStreet) - In view of rising oil prices and souring sentiment towards the nuclear energy industry, natural gas is back in the spotlight, driving investors into ETFs and exchange-traded notes targeting this attractive fuel source.The sudden spurt of popularity has created an alarming, albeit interesting scenario for one of these products: the futures-based iPath Dow Jones UBS Natural Gas Subindex Total Return ETN ( GAZ). As investors have poured into the product, GAZ has become increasingly disjointed from its underlying index. This has resulted in the development of a substantial premium that stood at nearly 18%, as of April 1. This inflated premium is due to the fact that no new shares of GAZ are coming to market at this time. In the latter half of 2009, in order to keep the fund from breaching limitations set by industry regulators, GAZ's managers intervened on the fund's creation/redemption process, capping its size. The recent popularity of GAZ has caused the fund to expand and once again is bumping against the limitations set up by the fund's managers. Unable to issue new shares to satisfy the heavy investor demand, the fund has essentially begun to trade like a closed-end product. This is far from the first time that the pricing of an exchange-traded fund has been tampered with, resulting in the creation of a substantial premium. In fact, earlier this year, investors witnessed a similar divergence occur in the Market Vectors Egypt ETF ( EGPT). After spending much of its time flying under the radar, EGPT got a jolt of popularity as Egyptians took to the streets in early 2011 to protest the nation's government. In response to the increasing unrest, the Egyptian government decided to shut down its stock market. In the wake t of the closure, EGPT's sponsor, Van Eck, announced that share creation would be halted until the market was reopened. Like GAZ, heavy investor demand, coupled with a halted share creation mechanism caused EGPT to break away from its underlying index, resulting in the inflation of a substantial premium. Weeks later, when the Egyptian marketplace was at last reopened and EGPT was restored to normal operations, the fund's premium was wiped out. As the fund fell back in line with its underlying index, investors left holding EGPT were sent for a wild ride.