If he's a day-trader, it's entirely necessary to keep funds in one's account. At least $$$ funds. The bitcoins can be transferred in and out easily enough, but dollars or other currencies often take days.
I don't think it's reasonable to expect an active trader to move funds in and out of their mtgox account every day. MtGox SHOULD be secure. If they are not, then we should stop using them.
Should be secure? Fairly sure MtGox has proven they are not secure. If you're still choosing to be a day trader on MtGox that's on you. MtGox isn't regulated. They don't have to meet security standards. You can't sue them (realistically anyway). It's not 100% clear who owns the parent company, where it's setup, and it's not backed by anything.
Again, he went on vacation? Even a day trader, I'd cash out. Second, he posted he left Bitcoins on MtGox. Then went on vacation.
Sorry he's retarded.