Three things have dramatically changed last 10 years:
1. People don't want to be sold - not as consumers or companies - but happy to buy and be served
2. We have 50+ suppliers (Salesforce, Dropbox, Yesware, Google Apps, Xero, Hubspot, ...) instead of a handful (IBM, SAP, Microsoft, ...) which means you pay a lot of companies little money each instead of few a lot.
3. Software is no longer sold as a "transaction" (sign-and-goodbye) but as a subscription (deliver value or see churn)

These three together make a perfect storm - sales people can't work like elephant hunters for 12 months on a deal, and when signed can pretty much deliver anything (hello Windows 2000 Server...). The game has fundamentally changed.

The new world is the one that Atlassian, Evernote, and yes, Slack show the way. Sales has changed to "Marketing" and "Customer Success" as the industry calls it. Marketing's job is to get people to find you, get to know you and want to buy.

If there is a sales team (and yes, most of these companies have them - I promise you - we supply to a lot of them - the call themselves "customer advocates", "product evangelists", or "customer success") they work with guiding the the customer to configure the product right.

There are new challenges though - as a sales person you are used to be able to talk to a customer and make sure that they get the product (and if you are smart, that it fits their needs). We have the issue that we get A LOT of new companies trying out our software, but never given the chance to communicate to them and educate them. It can be frustrating to see LinkedIn, Google for Work, Atlassian, Evernote, and many more appear in Mixpanel but they are not answering your emails.

We work hard on building the product to be more like a consumer product - meaning no manuals, no onboarding, no education, etc. It is tricky, but I think the new world of sales requires it. I at least am tired of signing up on a page and being called by a sales person just because I want to check out a new tool. And don't get me started on the hunt for a pricing page...

One last thing - it is a whole other story if you are signing bigger deals. Zendesk started as self-service but then hired sales people when they wanted bigger deals.