While I certainly agree that some people believe a reputable company should have their contact information available in the whois record and not use private registration. I also have realized personally the long-term side effects of having a standard public registration. You will receive both solicited postal junk mail and electronic E-mail (spam). Private registration give you the ability to legally mask your authentic whois record information. Effectively putting a proxy between your contact information, and a spammer. The spammer can still send communication to either your private registrars mailing address (c/o you, in theory the registrar should forward this written communication on to you, it certainly works for e-mail). E-mail is sent to a proxied address so it's important to keep your current address on file with your registrar or private domain service company.
In summary, private registration should not have any bearing on the reputation of a company. You would think, that if a business has nothing to hide, they probably don't need to use this type of service, but for one reason or another, they may choose to use this service.
I have had several domain offers or requests for purchase through proxied E-mail addresses on private domain services and had no issues, so people are still able to contact you very easily, and particularly if you're not someone interested in selling out on your domain, then you can easily ignore these types of solicitations.
ICANN? requires you keep your whois information up to date. This is harder for anyone but you to know if you have done this, but you'll get notices regarding this, and just do your part to keep your information current.