To be certain on revenue indeed.

I don't like it for the same reasons, but also because it feels like paying something on a loan/debt.

However you can resell such a contract. It is also not possible to keep your number if you go prepaid.

If they lack service as described in contract you can sue them and/or quit the contract.

And if they change contract (which some ISPs here have done since march 31 or april 1) they have to 1) tell this 1 month in advance 2) allow you to quit the contract.

At least, that is how it works here and AFAIK also in EU.

Overbooking, you mean. Yes, it saves them costs. But else your monthly fee for the connectivity & subscription would be more expensive. Then you might as well buy a T1 or E1 instead. If you read carefully -at least here- it says 'max speed X MB/sec'. If you're lucky it also shows a minimum. This is all nicely configured with some QoS rules at the DSLAM which is the bottleneck. The advertising of 'unlimited' referring to FUP I find more shady, and rather disgusting. Although understandable I rather know my data limit.

This is also why consumers don't have broadband. A 8/1 DSL connection is not broadband because of overbooking which is -at least here- typically between 1:25 and 1:40 on consumer DSL connections. So the heavy users are allowed to use their connection unless they start to compete w/the other. And each subscription gets a guaranteed speed. Those who pay more get more guaranteed. If you want better you get more expensive consumer subscription, business DSL, or SDSL (or FIOS) but you pay for it. You'll also get a SLA with some of those.

Those heavy users get kicked off because they breach 'more than 10 times as much as the average'. So they can kick those out if they use a FUP. Commercially, this makes sense. This is what Vodafone NL does, alhough they also provide uncapped/full speed 3G. Another example is T-Mobile NL. After 2 GB on mobile (smartphone) 3G you get capped to 384/64 kbit (it was 1024/384). IIRC their business subscription is unlimited (not even FUP; I know a journalist who easily uses 10+ GB each month). KPN, the third major 3G provider, provides all kind of packages; some optimized for static price every month, some optimized for full speed with variable price, some optimized for data limit. Each w/their own price and +/-. So I'd say there is competition, and there is choice provided for your interests.

Compare all this to the price of a 24/7 64/64 kbit ISDN connection and its heaven. Those went for like (converted from old currency) 750 EUR a month ~10 years ago when cable and DSL were still on the rise. And you had to get ISDN. This is nothing compared to T1 or E1! So the prices have really lowered a lot, and without overbooking, this would not have been possible. However, some ISPs provide a better/more sane overbooking than others. Even then, you probably pay for that. I know I do pay for that.