There are many quotes pertaining to usability on this site and for good reason. Usability underpins good user experience good conversion rates and more. Case studies on usability are typically instructive and this one is worth noting because the author makes use of a remote testing service:usability testers for hire. It works out well in this case but on a cautionary note there is something I call “professional tester syndrome” where people whose job is usability testing may not represent the average user and your results may be skewed.
If you’re going to use a remote testing service it’s a good idea to mix in some actual user tests. You can also conduct effective tests remotely using services like join.me and gotomeeting.com. The user may not be in the same room but they are live tests which you can record.