The increasingly high cost of text messaging has already caused a bit of a stir in Canada, and it looks like Democratic Senator Herb Kohl of Wisconsin is concerned with the situation in the US as well, with him now opening an inquiry to attempt to get the carriers to explain themselves. Apparently, Kohl is a bit puzzled as to why some customers are now paying 20 cents per message when they paid just 10 cents in 2005, a period that Kohl notes just happens to overlap with some consolidation in the wireless industry, when the number of national carriers shrunk from six to four. Those carriers, as you might expect, aren't saying much just yet, with Sprint only going as far as to say that it looks forward to "responding to the Senator's inquiry about the text messaging options we offer our customers and we will fully cooperate with his request," and the rest saying even less.