Depends on how long the thing is. If it's a 30-to-60-second spot, then 10MB is perfectly okay. I do them all the time. Compress the piece into an MPEG-4, H.264 codec, 1000 to 2500 kbps at 44.1kHz Mono.
Also, for FTP-phobic clients, try www.yousendit.com. A lot of people don't understand FTP or FTP software (eg. Cyberduck or Fetch); YouSendIt sends them an e-mail and they download the file from the web.
www.derekmok.com