That's why I can't comprehend companies using SaaS solutions like Slack or HipChat for something as crucial as internal communication, that requires a connection to an external server to work. What's even more scary is the data leakage risk - with DDoS you know when something bad happens, because the service simply doesn't work, but with data leakage how can you tell? Every single conversation stored on a 3rd party server. It's ridiculous. Yes, they're well protected, but it's also much more inviting for hackers - once you breach it, you gain a massive amount of sensitive data about thousands of companies... Well, it seems nice UI and 3rd app integrations are more important than security and reliability these days I guess.
If you are, say, a startup with sensitive information being discussed in an IRC server that you run, do you really think your data would be more secure then? Keep in mind that you can't afford a security expert (or your own time) to admin your system if you're a small business.
As for reliability, I've been using Slack for months without a single outage. If it went down for a day, the impact would be minimal -- I'd just use email and communicate less for that one day. Or I'd switch to another provider. Big deal.
How about P2P connections, so nothing leave your company's internal network, because why should it? It's the most secure and reliable solution, but even running an IRC server on a local machine is so easy that you don't need an admin.
You assume that every company has the knowledge and resources to provide an alternative which is more secure than what a 3rd party would be able to do as part of their core business. This, unfortunately, is not always the case regardless of the company being a startup or an enterprise...
What about solutions like Dropbox or Gmail? Or even plain old email for that matter. Even if you look after those yourself, how can you be 100% sure that you can offer a service that is more secure and reliable than a third party?
