Salesforce registers .com domains corresponding to each of its instances.
When you log in to Salesforce.com, you land on an instance, which is a subdomain of salesforce.com. As explained here, if you arrive from North America, your browser might load na1.salesforce.com.
Other subdomains include AP# for Asia Pacific, EU# for Europe and CS# for the sandbox environment.
You can see a full list of the instances and corresponding subdomain identifiers here.
Yesterday, Salesforce registered over a hundred “typos” corresponding to each of these instances. For example, na1salesforce.com for na1.salesforce.com and cs67salesforce.com for cs67.salesforce.com.
I don’t currently use Salesforce, and I’m not sure if people end up going directly to one of these instances through bookmarks. That would be a good reason for Salesforce to snag these domains. Another might be to cut down on phishing attacks.