1) Yes, you can download a trial version as Zalthor points out. I'm trying to work with SAP to make this more open and easy to do. It's important.
2) SAP customers vary from 1 employee (SAP BusinessOne) to 250,000+ employees (SAP ERP). But from a download perspective the interesting stuff is coming with Gateway and the Unwired Platform. With those tools - the server components of which will be available in the cloud - you can build Edge/Web Apps and Mobile apps using whatever tech you want. Ruby on Rails, iPhone, whatever. That's the sort of open integration which I hope will interest this audience, not downloading copies of SAP ERP for home.
3) Couldn't agree more, don't block social media at work. I wouldn't work for a company that did. By the way, SAP encourage social media and have 50k+ employees. But some organizations are stuck in the dark ages.
4) Streamworks integration is coming for the mainstream soon. It will be PaaS, integrated with the new Java environment and developer toolkit and supports open integration. It's had a bad press so far. Hopefully this will help.
Hope this helps.