Actually, I found a way to help people without them actually having to send me their accountname/password. If you're logged in and select a game, the address generally looks like this:http://www.pogo.com/
****/roomtabs.jsp?game=*******&site=****<key edited out to abide by site rules>.
I logged in on my laptop under a regular account I have, and emailed myself the key. On my main system, I clicked on the link in the email, and it opened up fine. I was able to get in & play, but wasn't able to change password, access account information, etc... without entering a password.
I just finished helping a friend out with some Stellar badges using this method. About the only thing I could see someone doing is affecting tokens by dumping them in gambling games, annoying people on your friends list, or spamming others. Once the person is done with whatever they were helping you with, make sure you change your password. I believe that the key is an encrypted combination of username & password; that way, you won't have to worry about them wreaking havoc in the future.