Has liquidity ever been a problem for you with Bitcoin investments? I would imagine limited supply and short term spikes could result in filling currency trade orders at lower prices. In other words, it's not clear if you can always depend on selling at face value.

Yeah, but quite a relative issue depending on the exchange. The first thing you learn is that you can't sell at market prices, you just have to place some orders and wait. To be honest I made a few mistakes related to this when I was starting and lost some money. On Btc-e my orders aren't that large so there's nothing to worry about when placing them. It felt more risky on Bitstamp, and Kraken specially due to low volume, but I rarely have to trade there.