Two extra things come to mind:

1) Don’t forget that there is also potentially a strategic benefit to Social Media.

Everything in that presentation seems to be about tactical benefits – which are essential in getting any new initiative accepted.

But things like creating better products as a result of better dialogue with customers are more strategic – in the sense that:

a) it will take a while to show any fruit (new products often don’t show ROI immediately, or even in their first or second year)

b) gaining better dialogue with customers may result in a repositioning of the company and a shift in brand capital – which again may not be easily discernible (people realise the company is now on the ball; but this may not yet translate to better buying decisions, and not to ROI).

2) While the logic of giving projects support based on ROI is sound, many projects are justified on a rather different basis – gut instinct and desire. Depending on the scale of the relative spend it is always quite easy to justify a project with a little smoke and mirrors and a lot of enthusiasm, despite what people may say.

In my experience, if you are working with senior folk in an organisation, often those with proven track records, they may not need to perform detailed cost-justification of projects at the leading edge. If they did, competitive lead would be lost.

Many senior executives know this and will often allow trusted people to take a punt on good stuff – even when ROI can’t be proven.

As you say extablishing causation is the really tricky bit. That said, for years organisations have spent money on branding campaigns which are similarly difficult to establish direct ROI on but show benefits in areas such as brand affinity, overall turnover etc. You just need to be as persuasive as a brand martketer in the mid-80’s (minus the turtle neck sweater) ;-)