With most stocks, you are limited by the fundamentals of the underlying security. With bitcoin, your fundamentals are based on making a new store of value and currency. It's almost limitless and the primary driver is exposure and the belief that it is going to happen. If you drive the price up buying, you will create that exposure. It's a self-fulfilling prophecy!
Correct. Bitcoin is a Veblen good, like gold, with a recursive virtuous cycle based on its own price. The higher the price goes (as long as the moves are slow and steady), the more people will believe in it, the more they will buy it, and the more the price will rise. Marginal demand is potentially infinite.
http://en.wikipedia.org/wiki/Veblen_goodAs to how to create a sustainable mania in any market, surreptitiously: human beings are like rats. They won't trust big sudden changes, but they will believe with religious zeal and become very confident if a trend is confirmed consistently, day after day, with no significant negative feedback. So the best way to manipulate a market to the upside (assuming you've got the funds in reserve) isn't to spend money pushing for new highs, but to lend constant support on corrections so they never develop into anything too long or major. For instance, using this approach, the US Fed has created a 30 year UST bond bull market with a captive brainwashed audience which, rat-like, keeps pushing the "buy" lever, unable to conceive that on the 15649th push the spring will release a sharp blade that will slice them in half.