I don't mind if they make it where it will always be voluntary with no chance of it ever being other than that. But it can end up being like Social Security cards.
First they were just cards that let you know what your number is. Could not be used for identification.
Now you can't get a job without them being able to photocopy your SS card.
Unless there are strict controls on this, it'll pan out like this probably.
2002: voluntarily get implant
2005: still voluntary but urged to get it
2007: things are restricted to you unless you have an implant
2009: can't really go anywhere without your implant
2010: ATM's scan for implants. Cannot use it otherwise.
2013: Opinion of those who don't have an implant is low. You're a nut if you don't have one.
2015: can't get a job, buy stuff, or do anything unless you have the implant
It probably won't happen for another decade or even two decades. But I'm 110% sure that in my lifetime it will become a requirement to get one of these implanted into you. The technology is here, now for the government to slowly require you to put it in you.