Yes, this is exactly right. Using a separate service like tumblr or blogger for your business's blog is fine. Hell, it's even smart, because unless you're in a

Yes, this is exactly right. Using a separate service like tumblr or blogger for your business's blog is fine. Hell, it's even smart, because unless you're in a rare situation where an atypical blog is a central feature of your site (like, say, Less Wrong), you should let someone else worry about managing the blogging software. But you absolutely need to have your web developer integrate it properly with the rest of your site. Pointing the DNS over to the blogging service is a fine little trick for making everything look professional, but it is not half as important as making the blog feel like it's part of your website.