Bitcoins are probably a great long-term 'investment', but...
1) Many people have good reason to not trust MtGox.
2) Go back to #1, it's a huge problem.
...
When we look at Bitcoin in terms of expected value, the odds are thus astronomical. The only reason Bitcoins don't trade for 100k USD right now is because...
Some of us remember May/June/July 2011, so it's a wise idea to sell some into big rallies, or BETTER yet, spend some BTC and/or help build the economy with useful projects.
Haven't logged into my MtGox account in over a year. I've bought and sold many bitcoins in that time and find the alternatives to be quite good. I don't see how not trusting MtGox is a huge problem. I hope they lose more trust and marketshare.