This is an interesting article that addresses that topic (Look at item #7):
https://news.21.co/thoughts-on-tokens-436109aabcbe
If you don't want to click on some random link in a post, you can search for "@balajis" on medium and find the article as well. :)
There are three links at the bottom of section #7 that refer to some guidelines that have been worked on over the past couple years as well as a worksheet to help you determine how likely your token is to be considered a security.
To be clear, it helps to understand where the really gray areas are, but there's still a lot of uncertainty.