We faced a problem with our Lordmancer II Slack channel. There were many scam messages every day: in private, in general channels, etc. We constantly banned those spammers, but they just registered once again (even the names were the same!). Also each day we saw new members with names like "CEO", "cofounder", etc.
Finally we dicided to close the Slack channel. Now we use Telegram group
https://t.me/lm2ico as a main communication channel.
I strongly recommend not to use Slack for ICO campaigns!
Well, what's the purpose of asking members from bitcointalk to third party apps like slack and telegram is something I cannot figure out. Have seen a lot of ICO asking to join their channel, but what prevents them from corresponding with participants in this forum itself, which would have been more transparent?