Yes, but in grand scheme of things, this is more a matter of etiquette then anything. Unless you are the first group out in the morning, think of how many people likely already set foot on any given spot on a green during the course of play on any hole during the day before you get to the hole.
That being said, it is a matter of etiquette that I personally feel is worth preserving if you have paid a large sum of money to play an especially nice course or are in any competitive setting, then you are well within your bounds to ask the offender to take more care when walking around the hole.
There is no reason for it to become confrontational, simply asking the offender to please observe standard golf etiquette is typically enough to embarrass the person into watching where they step. Should they have a problem with it, tell them you assume then that they don't mind you talking in their back-swing either, they'll get the message.
Then again, if this just a friendly round with a bunch of friends with at worse a beer on the line or a cheap round at a municipal course where the greens will probably be SMOOTHER after someone steps in your line, say thank you and putt away.