I don't know what to say

[Treesh]

It's actually against Blizzard's EULA or maybe the TOU instead to share your account with other people (except for your young children if you are a parent). Now, whether or not they can enforce that rule is another matter. ;)

Edit: It's the Terms of Use (TOU) that prohibits it.

A. You may establish one (1) user account ("Account") with which to play World of Warcraft by accessing Blizzard Entertainment's proprietary on-line service ("Service"), pursuant to the terms, conditions and restrictions contained in this Agreement. In order to establish an Account, you must be a 'Natural Person,' who is over the age of eighteen (18) years old or the age of majority in the country where you are a citizen. Corporations, Limited Liability Companies, partnerships, or any other form of legal entity other than that of a "natural person" may not establish an account, and by accepting this Agreement, you hereby represent and warrant meet these eligibility requirements. You may not share your Account with anyone, except that if you are a parent or guardian, you may permit one (1) minor child to use the Account instead of you (in which case you may not use that Account at the same time). You are liable for all activities conducted through the Account, including any activities which may be conducted by your minor children that you allow to use your Account.

And farther down in the TOU:

Your license to use World of Warcraft is limited by a number of factors which are listed here, and which are contained in the World of Warcraft End User License Agreement which you were required to accept when you installed World of Warcraft. Limitations on your right to use World of Warcraft may include, but not necessarily be limited to, the following:
<snip>
H. You may not exploit World of Warcraft for any commercial purpose, including, but not limited to, performing "power leveling" services to other users of World of Warcraft for "real" money.