Nothing has changed to keep something like 2008 from happening again.
Sure, it was a housing bubble that burst but it was the inbred, interrelated derivatives that exposed everything to the crash. That hasn't changed.
With the majority of the economic recovery going into wealth accumulation instead of back into the economy (via increased wages and spending) the US economy has little concrete to back the dollar except that it is linked to oil.
Weak oil doesn't mean a weak dollar, though. Oil is power - literally - so a low value of oil relative to the dollar means the dollar moves more stuff around the world. That's good for the US economy in some ways. If the price stays low for a while we'll see our prices go down and the real spending power of the average American will increase. That's good for the local US economy.
The potentially bad part is that it makes transactions in US dollars more difficult for other nations. That means making widgets in Korea from materials mined in Africa to be assembled in India before (finally) shipping them to Big Box Mart in the US becomes more expensive at each leg because transportation energy has to be paid for in dollars where the local currency is weak. This isn't a given. Its a function of the local currency vs. the dollar.
That cuts into the profits of globalized operations. So prices and profits of multinational products (electronics, appliances, some cars, etc.) are negatively affected but the prices of domestically produced stuff potentially goes down. That's GOOD for the US economy at the ground level but perhaps not so much for the upper level financier levels.
Its a tangled web, though. Who knows how it will actually shake out. I'm still trying (half-heartedly) to figure out why APEC did that and who benefits from it. And planning to fill my gas tanks before the prices go back up.