It's really simple math. What is the failure or success chance for Bitcoin? Do you think it will fail with more than 90% chance?
Current value is the sum over each scenario's price times its probability. With the success scenario having people who estimate prices above 100 USD, those people will buy at 10 USD as long as they see a 10% chance of a full success happening! That's not strange, it's perfectly logic!
The question is only of quantitative nature, especially concerning the full success probability and the value it will have if that happens. Both are not known, so everybody takes a guess.
You are absolutely right, but you think in terms of financial pyramid game! What you say about, is cheat, crime, but not the business. Difference is of quantitative nature - bitcoin IS the currency, and business field for the currency MUST include number of people, comparable with a typical large country.
Bitcoin is in its childhood? No problem! Just give a change to it to grow exponentially. Mining difficulty algorithm does not give such a chance. Bitcoin design is severe and totally damaged, I wrote how to fix it:
http://forum.bitcoin.org/index.php?topic=9487.msg155288#msg155288nobody cares. anybody plays in MtGox races..