If I own a domain (www.mydomain.com), what are the theoretical and practical limits on the number of sub-domains I can create (eg meta.mydomain.com, beta.mydomain.com)?
I think it's unlimited. For example, you can see
- wordpress.org: https://www.google.fr/search?q=site%3Awordpress.org
- or tumblr.com: https://www.google.fr/search?q=site%3Atumblr.com
When you create an account, you have your pseudo as a subdomain. And as you may know, Tumblr & Wordpress have a lot of members!
I found some interesting articles: