Deadlines are good for you; they give you an aim and push you to keep working on whatever it is you're doing. However, from time to time, you miss those deadlines for reasons out of your control (or just because you're lazy). Most of the time that doesn't really matter, you just push to get it done as quickly as possible. On the other hand, if that deadline was public you'll quickly gain a reputation of being unable to keep to schedules.

If hundreds of people are waiting for you to release the next patch of your program, and the deadline you've told them passes, they're going to get a tad annoyed and each day that goes by they'll get bored of waiting and just head to a competitor.

To counter this, you just don't release a deadline. Keep one to yourself by all means, but don't publicise it at all. Google have this policy to and never give a specific date of when a new product will be released. It's because of this people quickly forget that half their products have been in 'beta' for many years. We'd never know if Google had set Google Talk to be released before it actually was and so no one can say that Google isn't very organised.

Microsoft said that they were going to release elite features for Vista Premium users in January. They're still waiting for them... This was a massive thing when someone blogged about it and the entire world was like "Oh, that's really crappy of Microsoft!"

So, why follow Microsoft when Google is much better?