Thanks for your input folks. It's very nice of you to take the time to respond.

CedarS: As you suggested, I did bring this celebrity (Toby Keith) up in casual conversation. I hoped we would have an air-clearing discussion....and, rest assured, I did not use weighty words such as "obsession" and "infatuation".
I wouldn't say my wife was abrupt in her response, but I could tell she wanted me to stay well away from further discussion. I think her words were: "You like Billie Holiday's music, I like his music". Then she walked away.

I do think too, that from the nature of your helpful replies I've received here that perhaps I either need to explain the depth of the problem more fully or that you folks and I simply have different expectations of our marital relationship and vows.
I have a hard time seeing a "crush" on other person (whether the person down the street or some untouchable celebrity) as something that is "not a problem".
To me, part of what's important in marriage fidelity is what's going on in a spouse's head. If your wife or husband is fantasizing about being with another person and wishing to be with that other person more that you...that hurts. I'm sorry, and maybe I'm old-fashioned that way, but by the looks of some of my spouse's actions...she infatuated with another man...and to be honest, it hurts.
In addition to this I also think that based on how hard my wife is trying to hide her "obsession", that she is well aware that she's "outta line" and that she would be hurting me if I knew.
KathyM, it seems like your "crush" on JFK and your husbands "crush" on Selma H were out in the "open" in your relationship. Would your reaction be different if you happened upon your husbands "crush" accidentally? Especially if your husband very rarely mentioned Selma? What if you found evidence of him trying to get her home address? And what about if you realized he was trying to find out where she was on set and secretly planning trips to be closer to her? What if he started mentioning ways in which you could change your grooming, clothing and appearance...only to find out later that he wanted you to look more like Selma?
What I'm getting at here is that I think the idea of what you folks have in mind when you think of a "celebrity crush" is not what's happening in my life right now.

As CedarS suggested, I don't think the situation is as serious as my wife endangering herself or others. She is looking at real estate on Toby Keith's street though.