What's the alternative? Cash under the mattress? Or other (private) numbers in lieu of birthdate and Social Security number?
We're getting *way* off topic, but at least we've answered the OP question.
There's three ways of authenticating yourself, from weakest to strongest:
1. something you have
2. something you know (not recorded on paper or anywhere else that it can be "fetched" from)
3. something you are
Some examples for each:
1. a SSN or passport number, a card or a "token" authenticator
2. a password that you type into a computer or speak to a person (obviously, if it's spoken, it needs to be one-time-use-only)
3. a fingerprint, iris / retina scan, voiceprint, DNA or other biometric
Our society has decided that we're happy enough with using the "something you have" method of authentication for nearly everything that relates to our identity. Unfortunately, these numbers and documents (e.g. passports, credit cards, drivers licenses) are just too out in the open.
Then, when we hear of a government that's trying to secure this, usually with a national identification card (including biometrics), we're appalled at how the government is now going to know our every little secret and be able to track our comings and goings.
Ultimately, if you want to secure your identity, you'd SUPPORT any movement that changes us from strictly "something you have" authentication to a combination of at least two if not all three methods of authentication.
If, in order to identify yourself, you had to present a card, enter a password (not stored on the card, but in a central, secure, one-way encryption database) and also give a fingerprint or iris scan (also stored in a similar database to the password, though completely separate), then we'd virtually eliminate identity theft, not to mention the idea of forged travel documents.