We strongly discourage you from doing this. Anyone with access to your Google Account can access all the products tied to it. For example, if you use the same Google Account to sign in to DoubleClick DoubleClick for Advertisers and Google Analytics, someone who knows your Google Account will be able to view your information for both products. The best way to avoid information sharing is to keep your Google Account private.
If you had several users using the same DoubleClick Account, please have each user create his/her own Google Account to sign in to your DoubleClick product.