I have a coworker who is doing a trip to Europe next month. He very rarely flies, is not enrolled in any FF program, and has no plans to do so. Does it raise any red flags if I were to give him my FF number and have the miles for his trip credited to me? I don't know if they try to match up names on the tickets vs. names enrolled in the program.

(The flight is a SLC-NCE on DL, if it matters.)