I've had my account on Stack Overflow for more than a year now. Today, I followed a question that was migrated to Meta.
After I logged in, it suggested I merge/associate my Meta account with my SO account. (Simply brilliant that it was just a single click. Bravo to the dev team!)
When I tried to vote up these comments from before, I was then told that I didn't have enough reputation.
What's the point of having a minimum of 15 rep and having an account for over a year when I can't upvote on the other, related, sites?
Meta Stack Overflow is user support for the main trilogy of sites and the users of such should be able to vote on the ideas and feature requests that relate to those sites.
In the real world, if you had reputation, it would stick with you wherever you went.