Recently, Jumpgate Evolution was pushed back to an unknown date later this year. Although it wasn't a surprise to anyone, why would NetDevil keep players on the hook so close to the previously announced date? According to the devs, JGE was set for early June, but it was obvious this couldn't physically happen.
Let's get a quick thing out of the way first. Development teams use internal dates to mark deadlines for work to get done. They have their own date to when a game should be finished. This I have no quarrel with, it's a needed part of the development cycle.
What I am against is having release dates announced to players, but will inevitably be pushed back. This happens less frequently on single player releases, simply because there are less things involved and less problems to solve. MMO's are greatly afflicted with release dates being pushed back. Champions Online was set for June, but now it is past August. JGE has no known release date anymore. There are a few others but I don't care to think of them right now.
Release dates provide intense amounts of pressure to the team, but for MMO's its maybe a bit less than that of consoles. Consoles releases are more rigorously scheduled, especially with the titles releasing on the same day of its movie counterpart. This schedule occasionally forces teams to make decisions compromising the game's quality and overall polish.
So what should be done? In my perfect world, we shouldn't have release dates until, at most, a month away from release. This is usually about the time the discs are going into production and not much can be done. If I visit a game website and on the FAQ their answer to a release date is 'When it's ready', I am relieved. Which would you rather have? A release date a month and a half down the line, which is pushed back another two months, then another month or so, then after the holiday season? Ignorance is bliss, I'd rather know when it won't change.