Talk about your bad timing. Some Grand Central users who thought they were reserving a unique free phone number for life are now being switched to new numbers, just weeks after Google (NASDAQ:GOOG) acquired the site. According to TechCrunch, severalbloggers are chiming in with notices that their Grand Central numbers will be changing over the weekend.  

Grand Central gives registered users a single telephone number that they can use to manage all of their existing numbers. The service lets them route calls through landline and wireless receivers, take messages, record conversations, and even set ring tones.

But Grand Central is also a free service, so why are users looking a gift horse in the mouth? Well, trust is a big part of providing any kind of service. If you have a Yahoo! (NASDAQ:YHOO) email or Microsoft (NASDAQ:MSFT) Hotmail account, how would feel if one of those services replaced your email address? Don't even get me started on how social-networking addicts would freak out if Facebook or News Corp.'s (NYSE:NWS) MySpace begin to rescind the short Web addresses to profile pages.

Yes, Grand Central is free, but consumer expectations are far greater than what "free" might suggest. The rub here is that Google apparently had nothing to do with the switch. It's a problem with one of Grand Central's carriers.

To date, the only real change that has happened since Google grabbed the Grand Central keys is that the ability to upload sound files to create unique ring-back tones is toast. Users must now choose from a selection of licensed audio files. It wasn't a popular move, but it made sense. The last thing a huge public company like Google needs is to have record companies chase it down over illegal uploads or have its reputation tarnished by obscene sound files. Google already has its legal eagles tied up with YouTube.

However, Google must also now find a way to inject confidence in the Grand Central service. Users will be hesitant to promote their Grand Central primary numbers -- whether through acquaintances, personal websites, or business cards -- if they know they're just a carrier switch away from a major contact revision.

Once someone invests time in a free service, it's no longer free. Things can get costly indeed. Put another way, you can still get less than you bargained for in a gratis service.

Google's recent telephone buzz:

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Longtime Fool contributor Rick Munarriz is a huge fan of Google, and it would be his homepage if it weren't for taking up that piece of real estate. He does not own shares in any of the stocks in this story. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.