I am building a shopping site and want to know if building true MicroSites, with multiple target pages has any advantage over a series of landing pages. Would I suffer from any type of link dilution if I push out a series of target sites rather than one overarching one, or will I get better rankings by being focused?
I think there are advantages to both. The company I work for create what they call MiniSites. They are simply branded Domains and SubDomains. So our main site might be widgets.com and we have MiniSites like foo.widgets.com, bar.widgets.com and foobarwidgets.com.
The benefit of the MicroSites is that you can own and control multiple domains that point links to your domain, you can brand the MicroSites so that match more specifically to what you are trying to promote without the overhead of using your main sites design, and you are using those extra domains that you probably already own or should own that are related to your company. Also, you can link the MicroSites to a landing page within your main site, and just not do any advertising to the Landing pages.
The biggest downside of the MicroSites is that there is now competition out there for your main site Landing Page. What I mean is your MicroSite may not get the same level of page rank as your main site because it doesn't have the additional content and it could reduce the page rank of your main site landing page by increasing the competition. This would be somewhat offset by the link but who knows how much. All that means is if you only used your landing page in your site it might get ranked 4th in a specific search but with the MicroSite maybe that Landing Page becomes 6th and your Microsite is 9th. So you lose some but gain some.