I think the Marimba Effect is the key point. You've highlighted a problem with the original submitter's question: It focuses too much on how the competitors will react when you announce an idea before shipping a product, whereas the primary concern should be how the customers will react.
I just watched a talk by Mac developer Wil Shipley, whose advice is "Don't announce until it can be downloaded. Don't let it be downloaded until it can be bought." Otherwise you spoil a lot of perfectly good hype.
There are, of course, some exceptions to this rule in the webapp world -- for example, if you're starting Ptacek's social calendar for pets, you can't even build the product without having customers, since social networks without members are completely useless. So you're forced to bootstrap.
I just watched a talk by Mac developer Wil Shipley, whose advice is "Don't announce until it can be downloaded. Don't let it be downloaded until it can be bought." Otherwise you spoil a lot of perfectly good hype.
There are, of course, some exceptions to this rule in the webapp world -- for example, if you're starting Ptacek's social calendar for pets, you can't even build the product without having customers, since social networks without members are completely useless. So you're forced to bootstrap.