Note that most existing open source software is COTS, as it is licensed to the public. Some claim that fact invalidates the loss-of-control argument since the source code is available. The other school of thought insists on broader meaning of the loss-of-control argument, equating it with loss-of-functional-control where control is not defined as 'access to code', but 'realistic ability to manipulate the code.'
The motivation for using COTS components is that they will reduce overall system development costs and involve less development time because the components can be bought instead of being developed from scratch. Many considered COTS to be the Silver bullet during the nineties, but COTS development came with many not-so-obvious tradeoffs - overall cost and development time can definitely be reduced, but often at the expense of an increase in software component integration work and a dependency on a third-party component vendor.
Several groups have been formed to encourage the development of COTS systems for various purposes and promote their adoption. The Mountain View Alliance is one such group.