What policy should you have for not accepting an invitation?

Your choice, based on personal preference. The invitation the question is referring to is from the site LinkedIn. Not only is it a website, but it is also a mobile application. It was founded in 2002 but launched a year later in 2003.

The site is for employees to network with one another. Employers also use the site to view public profiles and fill positions. An invitation on LinkedIn is like a friend request on Facebook. It is to like two users together and the discretion whether to accept or decline an invitation is solely up to the user.