What happens when your sysadmins say "Maintaining IRC is a waste of time and gets us 1% of the features Slack does, let's just get Slack?" (At my last company, it was the sysadmin team, including myself, who decided to switch to Slack and killed our IRC server.)

Do you stop trusting them then?

2 sysadmins will cost considerably more than a few slack accounts. Unless your company is huge.

> Unless your company is huge.

Yes. Someone above have mentioned ibm using slack though. I think that's huge enough for the argument.

Yes at that scale it may be useful to roll out a custom system. However I'd count into account that large customers probably have different pricing and that maintaining custom systems is always bothersome because you are always the largest customer.

"Well funded sales team" is unfortunately what makes closed products win over open ones.