According to the dictionary it is correct usage to meet up with someone

( Enigmatic ™                 Voice No More                  ©, Mon 11 Aug 2008, 18:12, archived)

Fuck the dictionary.
'Meet someone' means the same as 'meet up with someone' and is less tedious.
( Bob Todd whee, Mon 11 Aug 2008, 18:13, archived)

Personally "meet someone" means something more general
And "meet up with someone" means a specific time.
( Pickle Fairy is clumsily dancing away this fear, Mon 11 Aug 2008, 18:14, archived)

yes, this is confirmed by the dictionary
to meet up means it was pre arranged as well
( Enigmatic ™                 Voice No More                  ©, Mon 11 Aug 2008, 18:16, archived)

I hear that Todd refuses to fill in forms
she will only fill out forms.
(rnuk http://flickr.com/rnuk, Mon 11 Aug 2008, 18:28, archived)

you meet someone by chance,
you meet up with someone on purpose.
( Moon Girl Technologies horrendous beanbag, Mon 11 Aug 2008, 18:15, archived)

WE MUST ALL STRIVE FOR EFFICIENCY IN OUR SPEECH.

(MooCow_Byter, Mon 11 Aug 2008, 18:19, archived)

let's all learn Japanese.

( Moon Girl Technologies horrendous beanbag, Mon 11 Aug 2008, 18:20, archived)