No real way to hide from those you want to ignore now.
Then, umm, don't add them as friends.
BBM has statuses for delivered (the message has arrived on the recipients device) and read (they have actually opened it). It's very very useful. You know at a glance where a conversation stands, you never have to "follow-up" to check a message arrived, you know if a message isn't in state D not to bother because they'll be out of reception, etc. It basically makes a BBM conversation much more natural than on SMS, or any of the big chat networks.
Then, umm, don't add them as friends.
BBM has statuses for delivered (the message has arrived on the recipients device) and read (they have actually opened it). It's very very useful. You know at a glance where a conversation stands, you never have to "follow-up" to check a message arrived, you know if a message isn't in state D not to bother because they'll be out of reception, etc. It basically makes a BBM conversation much more natural than on SMS, or any of the big chat networks.