Non-publication requests: Patent non-publication requests can be an important part of your IP strategy. Under US law, patent applications can be filed with patent non-publication requests. When this request is made, the USPTO will hold a patent application secret (i.e. will not publish it) until when and if the patent finally issues. Otherwise, absent this request, the patent office will automatically publish the patent application 18 months after the initial filing date.
When to consider filing a non-publication request: Non-publication requests are particularly appropriate for certain types of software patent applications, such as “business methods” and related software patents. This is because the US patent law for this type of software is presently in an unsettled state, and the international acceptance of this type of patent is also more limited. By filing with a non-publication request, your disclosure remains a trade secret. If the USPTO grants you a patent that is broad enough to be worth disclosing your work; great. If not, then you can continue to elect to keep your work hidden from the public.
When filing a non-publication request may not be appropriate: If you have plans to file outside the US, then by international treaty, you must file for international patents within 12 months of your initial filing date, and also allow your initial application to be published within 18 months. Here you can either not include a non-publication request on initial filing, or alternatively send in another form rescinding your non-publication request.
Other considerations: Unless a specific reason for non-publication can be identified, I generally recommend filing using the default, “publication” mode. This is because published patent applications can be useful. They help provide published prior art to help establish priority over patent filings from competitors. Additionally, published patent applications look impressive to investors, and can help give you more credibility.