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Mark and Francisco are both providing valid reasons to keep it part of the main domain.  There are other reasons to split it out as well though, beyond "in case you want to sell the blog at some point".  First and foremost if the primary objective is to build additional paths for potential customers and related to that, establish yourself as an authority on the subject matter in a broad sense, that's great - the blog belongs in a /blog folder of the main site. Be sure however, that you really do write content relevant enough and "on-topic" enough to keep it highly related to your target market and your product vision.  Too often I've seen blogs end up meandering into "related" topics that aren't truly related enough to be a very good match - they become diluted. If the possibility exists in a big enough way that the subject matter could grow beyond your primary market, in that scenario, it's much better to have a separate unique domain for the blog, because a diluted blog will ultimately dilute the main site's topical focus and intent of visitors. IF you split it out OR keep it in a /blog folder, either way, be sure not to over-link from blog content into the main site.  So don't just make blog articles that talk about new products and duplicate product descriptions, don't put more than one link in articles that point to the main site's products. Be sure each article has very high quality content that really does offer valuable information in its own right.