Silo architecture and PR dilution! What's real?

[vtmoz]

Hi all,

Today I have gone through this "Silo" concept where we need to build 2nd hierarchy level pages and then lower hierarchy pages further to rank good for related terms of "keyword(s)". But I wonder, is it real? the so called Silo structure? Google may consider that we are trying trick if we create multiple pages (doorway pages) targeting same keyword. And one of my competitors is having too many 2nd hierarchy level pages against this Silo structure and even the homepage rank may dilute by contributing to the so many pages. But their web pages rank good for the keywords they chosen by creating multiple landing pages. These are contrary to each other. How it works in real?

Thanks