Updated Sept 3: In the last week, Google has changed their mind on whether or not it is okay to link to a 3rd-party website on your G+ Local page.
As per the Google My Business guidelines:
Do not provide phone numbers or URLs that redirect or “refer” users to landing pages or phone numbers other than those of the actual business, including pages created on social media sites.
I was always previously confused on whether it was okay to link to a Facebook page or Yelp profile if the business didn’t have a website.
Marissa Nordahl, the Community Manager over at GMB, had initially said on this thread that “Facebook pages would not be accepted per the updated guidelines.”. Then a few days later, the Map Maker Team posted an updated response (after much discussion):
Q1. “Should we remove/deny a website that the company has created but is hosted under a service provider domain? A well-known example is Eataly, where La Pizza & La Pasta has their website listed as http://www.eataly.com/us_en/
A1. No, that would not be removed. We consider those “3rd party hosted sites” and approve them if the content is controlled by the place and there is no better, domain-owned authority page available.
Q2. “What is a social site? Yelp? BBB? Facebook?”
A2. A social site is a third-party website that has been created and hosted by a separate business but the content is controlled and maintained by the business in question. We do allow Facebook pages on listings if there is not a better / more direct webpage owned by the business. (It is important to note, that while we allow FB listings, we never extract information from them.)
Q3. “I know my local paper, part of the Hearst Corporation, also offer similar services creating a one-page website, under the local paper domain registration. Are all those websites to be removed from the Local pages? Where is Google drawing the line?”
A3. If the content is controlled and maintained by the business, it will be approved.
Q4. “There is a company that creates landing pages for home care companies as listings in its own directory site. (Example: http://elderpages.com/
A4. Yes. We would allow elderpages as long as the content is controlled by the place and there is no better, domain-owned authority page available.
So in a nutshell, if the business does not have a website and the directory/site has content that is controlled and updated by the business owner, it is okay to use.