just the same load / performance testing scenarios ... just generated from the "Cloud"
using cloud based servers is more cost efficient per virtual user as u are changed only for the bandwidth us consume ... and the time cost of setting it up.
Open source tools can be used or you can use loadstorm, browsermob etc to manage the load...
As most of these scenarios are on the web the major issue would be around simulating load on a like for like production system from an external source ... many large clients may struggle with this scenario (security issues etc) but the cost benefit would pursued them ;-)
Julia. Performance testing with cloud-based load generators, and analysis tools that can keep up, are changing how performance is optimized and driving tremendous innovation in Performance Engineering.