I use SO and have an account there. Occasionally I would visit meta without an account. Yesterday I created an account on meta with the same username and open id that I use on SO. A friend just told me I should have received 100 bonus points on both sites. I searched meta and it appears at some point this was true but is it still the case? I do have more than 200 reps on SO.
To get bonus points, you need to associate your accounts (see this page for your Meta account, this page for your SO account -- your user profile, accounts tab). The system uses your OpenID to know which accounts are eligible for associating, so you need to make sure you used the same OpenID on both sites.
Finally, bonus points are only given to users with accounts above a certain amount of rep. This Meta answer indicates that amount is 200 rep.