When the price of oil is relatively high, this encourages investment. Investment in oil is a long-term proposition. You can't suddenly reverse investment made in enhancing the supply of oil. These are big, lumpy investments that will extend far into the future. In response to the 1970s oil difficulties, there was a lot of investment made to increase supply, which ended up casting a shadow over the market for some time to come.
The issue I'm flagging for you is that we might be overheating investment in oil in response to these price signals, which have been partly inflated by speculation. Once we've committed to those investment decisions, we're going to have to build facilities intended to serve the market far into the future--this is oil that doesn't come today, it's oil that will come in the future--and perhaps that's not justified with the underlying economic fundamentals. So when you consider the landscape of the economy in general, it's a concern to be putting all of this emphasis on the oil sector, to the detriment of other sectors that might merit investment if this price signal mechanism weren't so distorted.