What Do You Do When You're Asked To Pre-Tip?

Eric suffered a traumatic experience at a smoothie bar that left him contemplating the very meaning of life. Or, at least, the proper protocol for customers asked to tip before any service is rendered.

He writes:

This is something that happened to me that brought up what I think would be a good post for your site. I know y’all have covered topics similar to this, but I feel like this one is the most all-encompassing and frustrating.

I was visiting Charleston, SC, and wanted a semi-healthy snack around 5pm to tide me over because I had dinner plans for nine that night. I walked into a local coffee house, and proceeded to order a strawberry and banana smoothie. Much to my chagrin, the barista had me pay before he made the smoothie, but this was only mildly annoying and I didn’t challenge it. He waited to ring me up before making the smoothie, so as I was filling out the receipt, I knew he would see whether or not I had left a tip. Part of me wondered if my tip at that time was going to affect how good my smoothie is, which ordinarily should be the other way around. I decided to leave no tip out of principle, assuming that the coffeehouse was personally trying to influence tips by that tactic. He might have not cared at all, and the smoothie wasn’t horrible, but it was an odd experience.

A corollary question is, what to do about tip spots on credit card bills at sandwich/burrito places? Aren’t they getting paid a to be “sandwich artists?” Similar to my first question, I wonder if workers at places where I frequent (and thus, they know who I am) will deliberately sabotage my sandwich to get vengeance for my lack of a tip when I shouldn’t be asked for one in the first place.

Are you an auto-tipper or do you lay down your own ground rules when confronted with the pre-tipping conundrum?