According to threads at both DigitalPoint Forums and Search Engine Roundtable Forums, MSN in the UK is showing that the search box is prefilled with "The Apprentice BBC." This was actually spotted this morning but I was able to reproduce it just now.
The screenshot can be seen below:
Barry blogged about it on Search Engine Land as well.
Is this a brokerage deal between Microsoft and the BBC? Danny is following up with both Microsoft and the BBC.
I'm not sure I'm enthusiastic about this implementation and would hope that it does not go further than this "experiment." It would be completely confusing to users who have no intention to search for anything related to "The Apprentice" or whatever else might end up being prepopulated in those search boxes. Even newer users will wonder where they are supposed to search now.
Update from Barry: To me, it is looking less to be an ad. More at MSN UK Shows More Prepopulated Kewyords in Search Box.