Let's say I have site A. All of the pages in site A are linked to each other. In the index page of site A, I have a link to site B, and vice versa. This is in fact a question about how engines measure link popularity, so if anyone can refer me to a few good, thorough articles about this I would appreciate it. Crawler behavior is prety easy to determine. If it only hits the pages you submit, then it isn't a deep crawler.
Most engines are a combo of the two forms.