what would cause the BTC exchange rates to rise?
FUND INFLOWS INTO THE EXCHANGES from existing and / or new users. To make the BTC/USD exchange rate rise, the economy needs around 8000 BTCs worth of inflows every day (160 blocks per day * 50 = 8000 BTC). This of course assumes that all miners convert all back to USD regularly and dont save bitcoins at all, which is not 100% correct.
Still, there needs to be significant money inflows into BTCs regularly as we know that miners need to offset their costs and pay off hardware, pay electricity etc.
What could make BTC rates fall: no further money inflows make the BTC/USD rate fall on its own weight (because of the BTC inflation due to mining)
This means that ideally every current bitcoin users should convince another new user to start getting into bitcoins.
Perhaps we can start a tell-a-friend mechanism where there are incentives for existing users?
We need more FUND INFLOWS. We know what supply is. Over 5 million in circulation and a small fraction of that floating. More currency exchange is what we need. More points of entry. The Bottleneck is the conversion of fiat into BTC and vice versa. it's too difficult for most people. Mt Gox is important but we need larger and more numerous points of conversion. That is the key. Goods and services available for bitcoin directly will help but the explosive growth comes from BTC/fiat convertibility and the ease with which that is provided.
Source code for Britcoin is free. You can either try to set it up yourself, or I will do it for 600 BTC. Or 2 people at the same time for 800 BTC.