Perhaps the folks at the "Open Government Initiative" assumed all 2.7 million or so federal employees (including the Postal Service) knew about their blog site and check on it everyday to find out what the important people who work there are thinking and writing.
Whatever the thought process, the White House did a great job of letting everyone know about the project and taking credit for being innovative, experimental, and edgy in their approach to using the internet and creating a 21st century government.
But, if they really wanted suggestions and not just a chance to issue press releases, the public relations folks forgot to let the millions of federal employees know how to submit their ideas. Perhaps they just wanted credit for setting up the program. Perhaps they thought their program was so important everyone in government knew how to find their blog site and was very familiar with the important work they were doing. Or, perhaps, in publicizing the program and how it would change the way government works, they just overlooked a couple of minor details.