Companies that use 'Google Apps for Business' are providing their staff with managed access to Google products for business use. That includes the six core apps (contacts, gmail, calendar, docs, sites and talk) but it can also include 62 additional services such as youtube and blogger.
The domain control panel allows the site administrator to force users to logout of the business account before using these services. This makes a lot of sense for companies who would rather their staff were not uploading youtube videos or blogs in the company name and is why I always recommend a 'default-deny' policy for additional apps.
If you do want your staff to use youtube, maps, blogger etc. in a professional capacity, you can always switch them on as required. Google do make it clear what account you are logged into when you access these services, so it should be clear to users in what name they are using these services , but thinking about the policy up front is always advisable.