@thomas k, this really isn't luck. Verizon runs their telecommunications network, well, like a telecom -- they actually try to maintain a level of service, they make large long-term investments instead of trying to stay like 6 months ahead of usage (or worse, like so many fall behind usage and then try to catch up), and they don't sell people service they can't actually provide just to make a buck.
I must give props to Qwest (my local telecom) for providing service as advertised too -- they have not rolled out fiber-to-the-home, but the fiber-to-the-node system they have, the fiber is reportedly VERY undersubscribed, and everyone I know who has gotten Qwest has gotten speeds as advertised. Where they don't have fiber, they are if anything excessively conservative in terms of saying "no your line is too long for this higher speed" too.
The big problems in the US are several:
First, for cable, they carry many many channels, a large number of analog channels and a large number of digital. So, there are only a few channels (like 2 or 3) available for use by all the cable modems in an area, and a cable node tends to cover at least a city block, and often larger areas than that. So there can be congestion even before the cable node. DSL avoids this particular problem, because each user has their own copper pair.
Secondly, there is the backhaul, this runs from the cable node to the cable company office, or for DSL from the DSLAM (local box all the DSL lines run to) to the central office. I've heard some DSL providers are quite bad in having inadequate bandwidth running to the DSLAM. I think cable has more problems from the home to the cable node than with backhaul, but I've heard of cable nodes having a lack of backhaul too.
Thirdly, some ISPs are perfectly happy to sell whatever service the customer orders, instead of what the copper can actually support -- if the phone line runs straight to the central office, or is old, or someone's in an apartment complex where the cable or phone lines are grody, instead of offering a stable 1.5mbps, or 3mbps or whatever, the ISP will offer like 8mbps anyway, and the line can't support that speed.
The first problem is hard to solve, cable cos will either have to reduce or eliminate analog channels, or switch digital channels to MPEG4. Both would require sending a new cable box to every subscriber, which is very expensive, in addition to whatever else has to be changed.
The third problem is either very expensive (run new copper or fiber to the home) or very cheap (test the line and don't sell service the line is incapable of providing.)
The second problem is the big one -- both cable and DSL companies are making far more money off internet service than off anything else. But, they are perfectly happy to keep offering faster and faster service to end users, while not reinvesting the profits to make necessary upgrades to their backhaul and backbone networks.