It is in fact not the case that there is a single exchange on which IBM trades (it is listed on the NYSE, CsE, and at various places abroad). Liquidity factually does exist in different amounts at different places; this is a major reason why HFT works.

Bitcoin is volatile because it has a small float, terrible market infrastructure [1], a relatively unsophisticated set of traders, a Wild West of market manipulation [2], and no fundamentals to get in the way of wild gyrations.

[1] The biggest Bitcoin exchange presently is functionally incapable of transacting in dollars.

[2] As one of many things that could be said here, the biggest Bitcoin exchange earns commissions in Bitcoin and then “dollarizes” then by selling the Bitcoins on their own exchange, to their customers.