At the very least then, even if they don't read any more, they will have been reminded of your company and this will make them more likely to consider your organisation in future. It's this logo that will attract the attention of the person looking at the card and so this needs to be fairly large and fairly central. Remember when most people look at your business cards, they're likely to be digging them out of their pockets after a night out, or finding them when going through their wallets. Hopefully the logo should remind them of the conversation they were having when either you or your member of staff gave them the card.
As well as a logo, business cards printing should also include some relevant contact details that can help the recipient of the card to get more information regarding your service.