When I think about prototypes, I almost always imagine some sort of high fidelity prototype. The debate about low fidelity and high fidelity is an ever growing one and everyone seems to have an opinion about which is better or worse, or useful or not. Prototypes are extremely useful as they are the look and feel of what the system will look like. High fidelity prototypes are as close as you will get to in terms of the actual system. I feel for the purposes of usability testing, it is better to have a high fidelity prototype in order to get the maximum benefit out of a testing with a prototype. In general users also feel much more comfortable working with a high fidelity prototype as opposed to working with a paper prototype. Low fidelity prototypes are a starting point into creating a prototype, but I feel that project teams can save a lot of time by building an efficient high fidelity prototypes instead. Creating one version of a high fidelity prototype instead of a series of low fidelity prototypes to reach to a realistic prototype would be much more ideal. As a user I would also like to work with a prototype that is as realistic as the actual system or application.