Ok, this comes up from time to time. Essentially if you feel we contributed intellectually to your project it is appropriate for us to share authorship. If not, then no we should not be authors on your paper. Usually it’s pretty obvious what side your project falls on, but if you have any questions it’s always a good idea to talk to us about it. We don’t mind.
If you want a more detailed explanation of authorship when using a core facility please have a look at the ABRF Authorship Guidelines. These are the community standards most core facilities follow when there are questions about authorship