Maintaining an up-to-date and informative blog is one of the best methods for a company to establish credibility among potential clients. It's also an excellent way to ensure search engine optimization efforts help drive a business to the top of Google and Bing search results lists. However, it's increasingly becoming popular for companies to host content that isn't their own.
The key is the guest post. When an organization creates its own content, it's clear to readers (as well as to search engines) that the author comes from a single company. Interestingly, SEO campaigns and readership are improved when a post is made by someone who is clearly from another business.
Credibility is helped because prospective clients notice the relationships that businesses have built. It also helps to connect organizations with common goals. Search marketing is aided because the sharing of links and information between two websites demonstrates that they've collaborated in a meaningful way that makes the internet a richer place.
Make sure not to confuse this practice with link sharing or affiliate programs. The former is a black hat method of simply trading lists of active links in the hopes that search rankings will improve. The latter is the hosting of content available across the internet on a subscription basis. Google and Bing have both taken steps to penalize businesses for these practices, so make sure that relationships and content trading are both personal and legitimate.