MtGox was not a normal exchange. The MtGox Bitcoin was essentially a separate entity from a regular Bitcoin. The MtGox Bitcoin was offering higher than normal rates of return. This encouraged investors to pump in new capital, which was used to cover previous expenses MtGox had accrued. They then would pick and choose who they would allow to cashout at a high rate of return to keep the ruse going for an extended period of time, while making excuses to others. This worked until the Ponzi scheme imploded. I know you don't like that word for MtGox, but the fact that it may have been a legitimate exchange at one point does not prevent it from turning into a Ponzi scheme at a later date.
I'll admit that not all the facts are known, and my conclusion above is essentially hypothetical based on the information known at this time. Perhaps when if we ever get access to internal communications within MtGox, we'll know the truth. Even pleading incompetence does not mean that the operators weren't unknowingly running a Ponzi scheme.
Perfect example of the mentality of a new investor at MtGox can be found on this reddit comment: http://www.reddit.com/r/Bitcoin/comments/1yw9vj/how_i_nearly...
I'll admit that not all the facts are known, and my conclusion above is essentially hypothetical based on the information known at this time. Perhaps when if we ever get access to internal communications within MtGox, we'll know the truth. Even pleading incompetence does not mean that the operators weren't unknowingly running a Ponzi scheme.