Can BeejiveIM for iPhone block unwanted add requests? I've been getting a lot of bogus contact add requests from my Yahoo account - it almost always turned out to be a spambots. I wonder if BeejiveIM has a feature that can block these spam requests? 

If that's not the case, what multi-protocol instant messaging client for the iPhone that can block out these spammers? Ideally they will automatically prompt for a captcha to the requester before showing me the request.
I don't have a Yahoo account to investigate for you, but I know that with AIM (AOL Instant Messenger) accounts you can change the security settings to: 


Allow Anyone
Allow People in my Buddy List
Allow Specific People 
Block Everyone 
Block Specific People


I would assume that logging into Yahoo! directly that you would have similar settings available to you. Then, no matter what client you would use on your iPhone when logged into the Yahoo! account, the settings you already placed into Yahoo! would translate over.