Oliver over at MobileCrunch has posted a glowing review of a new custom voicemail service called YouMail that allows cell phone customers to create unique voicemail greetings based on caller ID, so a person could have a unique greeting for significant others, business calls, ex's, family, etc.:

I see lots and lots of mobile applications. Some very clever, some less so, but few which I think will have the broad appeal and viral growth of YouMail a new application/company that has been incubated by Orange County, California based Zeacom.

It sounds like a fun service, but I question the potential. I wonder what the uptake of similar phone features like unique ringtones by caller ID, attaching photos to contacts in an address book that will show up when someone calls, etc. is? I have a feeling it's pretty low at this point and they're both pretty easy (and free) services. Does that give us any guidance about the potential for this service?

Of course, I could be wrong. This is somewhat different from personalizing your own phone's address book and ringtone since customized voicemails for friends as as much for them as they are for yourself. Will this lead to a viral uptake of the feature?