Is the Yearling badge meant to replace the Beta badge?
I was awarded the beta badge on stack overflow and now it seems to have disappeared from my list. Any ideas can you lose badges once they are awarded to you?
It was revoked. Pretty much because the terms of the Beta badge were more strictly defined a short while ago.
Basically, if you signed up during the Beta period, but didn't ask or answer any questions, you're no longer considered having, "actively participated in the private beta".
Active participation includes notching three (3) bronze badges on your belt before the Beta ended.
While you may have gotten a Beta badge previously, they have been revoked following the strict outlining of this description.