Another reason you may want to delay pre-launch marketing is that if you plan on patenting your product you can invalidate your ability to do so in certain juristictions (including most of the EU) simply by "disclosing" your invention.
If your landing page could be construed as an "offer for sale", and goes up more than one year in advance of your patent application, you've lost your ability to patent protect the idea in the US as well.
Of course most startups these days (the ones reading HN at least) are working on web apps and patents are not as commmonly employed. If you ARE working on a patentable idea though, you should do some research and consult with an IP lawyer before you go and put up any public marketing material before you have applications in to the jurisdictions where you want protection.
If your landing page could be construed as an "offer for sale", and goes up more than one year in advance of your patent application, you've lost your ability to patent protect the idea in the US as well.
Of course most startups these days (the ones reading HN at least) are working on web apps and patents are not as commmonly employed. If you ARE working on a patentable idea though, you should do some research and consult with an IP lawyer before you go and put up any public marketing material before you have applications in to the jurisdictions where you want protection.