As others have explained, YMMV is simply expression to say, "what may have been true for me won't necessarily be true for you." It's not connected to the mileage bonuses for the credit card, and you will find this expression used in many connotations on FT having nothing to do with miles.

However, now that you mention it, are you sure Continental still has the 50K bonus around? I signed up for it just before it went away, and now see the standard 30K + $50 credit.
Just to let you know, if you do get the 50K, you won't get any additional bonus for adding other users onto the account, nor will you get the $50 statement credit, through there have been people on FT who have requested and received the $50 credit. I requested it and was denied.