If you have one of those modern web\mobile apps chances are that testing a zillion combinations of cross browser\cross platform test is already causing you headaches besides burning hole in your pocket. Moving your test automation to cloud (or at least a part of it) can bring in several benefit to your organization.
Reduced Cost Made possible by pay as you go models
Faster testing made possible by parallel tests on cloud
Scalability made possible by on demand provisioning of resources