Buying up lots of domain names that are vaguely similar to your primary domain is common practice and lots of online business owners will have a stash of domains that they have invested in rather than simply buying just one.

In most cases where clients simply want to have multiple domains with keyword variations in the domain name, we usually suggest that’s not an effective strategy. But there are some valid reasons for registering multiple domain names.

Search Marketing Standard lists four specific reasons it might make sense to do so:

  1. Owning multiple domains can lead to more traffic
  2. Owning certain domain variations can be a strategic decision
  3. They can help you leverage domain complaints or domain reviews
  4. Multiple domains can handle misspellings of your domain

See the article in Search Marketing Standard for an elaboration of each of those.