A key question for European regulation going forward is the degree to which a third physical broadband access medium might substitute for broadband offered over traditional telecommunications and cable. Only if a third effective facilities-based competitor were to emerge would it appear to be practical to eliminate the current, rather intensive asymmetric regulatory obligations imposed only on network operators that possess Significant Market Power (SMP). The most promising option for this “third wire” is mobile broadband. A recent study for the European Commission revealed somewhat unexpectedly that the majority of broadband data originated by smart phones and tablets today (i.e. by the devices that we typically regard as mobile) is in fact transmitted over Wi-Fi, primarily using private Wi-Fi services at home and at work. By 2016, it seems likely that 80% or more of the traffic originated by smart phones and tablets will be transmitted using private Wi-Fi off-load. This has profound implications for fixed-mobile convergence. First, this result implies that most of the data that we think of as being mobile is in fact being transmitted over the fixed network (typically using the consumer’s Wi-Fi DSL or cable router). Second, it implies that fixed network back-haul capability plays a huge role in the transmission of data that we typically think of as being mobile. Taken as a whole, the data off-load ecosystem turns out to be much larger, richer, and more complex than expected. This assessment implies in turn that the ability of the mobile network to substitute for the fixed network is ripe for some re-thinking. The mobile network could not carry anywhere close to the load that consumers already impose on it without effective mobile off-load, which depends on the fixed network. The fixed and mobile networks are far more intertwined than has been assumed by most experts to date. Our preliminary assessment is that off-load implies (consistent with many other aspects of the mobile environment) that the mobile network is a significantly less-than-perfect substitute for the fixed network, and vice versa. This in turn probably implies that it is not going to be practical to phase out asymmetric SMP-based regulation any time soon as a result of convergence between the fixed network and the mobile.