I was setting up an ad campaign today via the web interface (IE 7), and in step 2 (ad creation) I noticed it tells you there is a character limit, but the interface does A)not limit you to those characters when you submit, nor B) show an active countdown of remaining characters.

I think adding those two features would take less than a day and save the users some time and effort. Right now if you go over you have to try and submit it again... still not knowing how long anything is.