When Hansel and Gretel laid down a bread crumb trail, the birds ate it and they got lost. The pebble trail is what got them home.
That's a great question - I have a post I've been working on for a while where the intro is:
The Brothers Grimm's Hansel and Gretel is a story of a brother and sister who are sent into the forest to look for food. The children leave breadcrumbs on the ground as a means of trying to create a trail to follow home.
Ironically, the breadcrumbs are eaten by birds and do not serve as a navigation guide for Hansel and Gretel. Are the web version of breadcrumbs any better in aiding navigation?
I tend to over-analyze so I have sources and other info I'm still coalescing. Most of it is still in note form. I hope to publish it within a month of relaunching my site.
Here are some of the sources I have put together.
I try to look at items like breadcrumbs from 3 aspects: UX, IA, & SEO. The article is more heavily biased in terms of SEO vs UX. Meaning - you can provide breadcrumbs and should, but beyond the basic text breadcrumb and location. Architecting your breadcrumb should be about IA and SEO.
Having said that - I have no clue when I will relaunch my site, but the most important information can be found in those links.