Last month it was Amazon which was supposedly keen to buy Sprint’s Boost Mobile unit, which it plans to divest to help soften regulators’ views of its proposed merger with T-Mobile USA. Then, last week, Google was reportedly in the frame via a tie-up with Dish Network, another likely bidder for Boost. Google quickly denied such an alliance, but the merry-go-round of speculation over the fate of a fairly minor part of the Sprint business highlights the uncertainty over whether the web giants really do plan to get into mobile connectivity, with disruptive impact on the US telecoms market. From the point of view of Sprint and TMO, although interest from Amazon or Google could push the price of Boost…