I would think anything over 10" on the front would be overkill. I am planning on 9.5 or 10's up front. I start to get concerned myself especially with handling on wet pavement. Big tires become skis very quickly. You may not plan to drive in the rain, but more than likely you will get caught in it. I plan to drive the crap out of my car and I know I will get caught somewhere on a trip.
There has to be a point of diminishing return somewhere for race application. Vehicle weight is something to be considered as well. Lighter car will turn just as well on narrower wheels. Narrower wheels equals more speed in the straight away due to less friction. Wider wheels require more turning radius. Very wide wheels require power steering coolers, more friction, more heat, harder to package. I was talking to Marcus at SC&C the other day and he brought up a good point. A stock C5 vette with race tires will pull right at 1G on 245's up front.
For street, all the wide front and rear tires end up mostly as awe factor. I can see the reasons for the wide rear tires with people putting 500-1000 hp motors in street driven cars. I know, I know, I am the pot calling the kettle black here with me putting 345 19's on the rear of my car! In the end it boils down to personal preference and taste and go do what makes you happy! Oh the decisions!
Mike