As a web designer my company website is always incomplete, I keep redoing elements of the website to make it more usable. One thing that struck me recently is after a user has gone deep into a site, does he go back to the home page or simply exit? Yeah I know analytics should tell me that, but there is something better.
This simple navigation guide could be the missing ingredient for that usability recipe you have just prepared. For websites that have more than a dozen pages, navigation should be given serious thought if you want your users to stick around. Can you imagine going around disneyland without those "You are here" signboards. Your website needs it too.
Theoretically the browsers back button is supposed to be enough to go back to where you came from. But imagine your user who reads your home page, then to your products page and then to your download page, and then to your forums page, now what?, should he go back every page to check your other products? Nah, he would rather goto youtube for that funny video.
Breadcrumbs leave a trial of where the users have been and help them get back home, as simple as that. But implementing breadcrumbs into your site could be a little tricky if you keep rearranging your site a lot. You could use java script to automatically generate a trail for you, or you could hand code it if you have a smaller site. Either way it works on your users, they know where they are and can get back to pages they have read.
Most importantly it increases the stickiness of users, making them read more, probably download more and then buy more?