If you are having a hard time ranking for longer tail keywords or more product specific keyword terms then siloing your content could be your key to success. By successfully siloing your content you can help GoogleBot understand what content is actually related to other pieces of content. Below is a quick graphical representation of siloing.
If the blog is about “tax information” then your main category landing pages would be your longer tail more specific keyword terms which link back to your main page. The smaller circles on this diagrams under “tax return” should talk specifically about “tax return” information and link BACK to the “tax return” landing page as well be under the FTP folder for “tax return” i.e. http://www.taxinformation.com/returns/fileyourtaxreturn.php/. This technique helps GoogleBot understand the content breakdown of these pages and can further help rank these internal pages for the desired keyword terms.
Bruce Clay is a big advocate for Siloing and has helped pioneer this idea. In an article about siloing that was written by Lisa Barone, she talks more in depth on the break down between virtual and directory siloing and examples on how each should operate and look.
Most blogs utilize this type of site structure technique but the problem usually is on the user side, producing duplicate content and improperly siloing content under multiple and incorrect categories. Graywolf put together a video about siloing your WordPress blog that I thought was pretty good and worth mentioning here.
If you are having problems ranking for long tail or product specific keywords then examine your site structure and if you are not siloing your content then give it a try and see if that helps your SEO efforts.