I called Cardmember Services and they agreed this looks like fraud. They are canceling my Visa and sending me a new card. All those Boingo charges are being reversed. I have to change my Visa card number on all the accounts I do business with now (like Orbitz and Amazon).
Boingo is basically a nuisance as it is, but now I think I will refrain from using it ever again, even if it's the only wireless available. Travelers, be advised.