I keep several different identities.
For example, on my domains' whois I always use a specific identity (with a valid email just in case someone needs to reach me, as well as a valid phone number).
And in business relationships I use different company names for different markets (Internet Marketing, Web Hosting, Domaining, Coding Services, Web Hosting...).
It helps separate both earnings and clients. And clients and partners get the feeling of that they're dealing with a specialized company, which is usually the best thing they could do.
The only disadvantage I can think of is the huge amount of time it takes to get used to all those identities (I don't use to trust anyone else my business).