Sustainable business model: The basic business model for uncapped accounts is simple: high end users who use tens or even hundreds of Gigabytes of data per month are subsidized by low end users who use less than 15 GB per month.
When things don’t work out as expected
In South Africa there is a pent-up demand for broadband bandwidth, and early adopters of uncapped ADSL services are often high end users. This can put strain on the business model of an ISP offering uncapped services, and this is when service levels start to slip.
Unless ISPs continue to allocate adequate bandwidth in line with the demands of their growing user base, subscribers will start to compete for highly contented bandwidth and slow speeds will become commonplace.
At this point ISPs may employ practices like traffic shaping, rolling thresholds and throttling high end users to try to provide an acceptable user experience to the largest portion of their user base.
In some cases an ISP will continue to sign up new subscribers without upgrading their network because of financial constraints, leading to very high contention ratios and hence poor average throughput.