A study by Federal Communications Commission, stated that ISPs aren't truthful in advertising broadband speeds, often choosing to use maximum connection speeds in attracting customers. "US broadband consumers in 2009 were getting half of the download speeds advertised by their service providers. In 2009, the median advertised download speed for US customers was 7Mb/sec and the average was 8Mb/sec. The actual speeds were at 4Mb/sec average and 3Mb/sec mean."
FCC is coming out against service providers advertising the maximum speed to potential customers. According to FCC, the "up to" metric that all providers give doesn't take into account congestion, network efficiency, website performance and various other external bottlenecks that typically clog up the Internet pipes and are outside the control of the ISP.
Reference: FCC Boradband Study