You can certainly do both.

Many bloggers use both a site-wide disclosure (a separate page that lists their disclosure policy in detail, which also often includes a contact email) as well as individual/per-post disclosures so that all bases are covered.

Other bloggers may use a site-wide disclosure and then put sponsored posts/product reviews in clearly marked categories and/or add tags/labels to those posts (like "Sponsored" or "Commercial Break" for paid or sponsored posts; and "Product Reviews" for product reviews).

For us, offering bloggers who simply use a site-wide disclosure the option to continue blogging about us as often as once a month is an effort on our part to clean up the look of some posts that are written about us. We're all for clear disclosure, but some posts are "overly" advertised/commerciali zed as such, to the point where it's a turn-off for readers. I think most of us are capable of distinguishing a sponsored post or product review from a "regular" blog update without needing four glaring disclaimers telling us so (especially if the blogger uses a specific category and/or tag for those posts - in my personal opinion this is a great and "classy" way of going about distinguishing as well as organizing such posts).

However, we're still working with bloggers who use individual/per-post disclosures. For the time being we just ask that those bloggers blog about us no more often than once every other month. less