Econ professor Marius Schwartz just wrote a short, yet incredibly useful analysis of competition in the Internet backbone space. You can find the AEI-Brookings publication here, but if you want the summary version it’s this: there is tons of competition and the SBC/AT&T merger won’t change that.
And here’s one bit you won’t want to miss regarding the Verizon merger:
Thus SBC/AT&T and Verizon/ MCI together would have less than 30% of Internet traffic. To put this in context, at the time of the Sprint merger, MCI by itself had a larger share – but still was unable to impose interconnection charges on fully eleven competitors!
Analysis of Internet backbone competition