So the weak dollar increases US exports - pretty clear why - However dollars are needed to buy these "cheaper" exports - surely this creates a demand for the dollar and will strengthen the currency?
2 problems:
1) the US produces very little things that the rest of the world wants.
2) more and more countries are looking to trade in anything but US$
1) just take a look at their trade deficit - they import sooo much more than they export
2) rumors about items that are currently traded in $$ may change to another currency like oil for example.