the bottom line is, if a company can spend $1 to earn $2 they will do it. if not they dont deserve to be in business anyway. Similarly, if I can spend $.50 to earn $1, I too will do it every time. To me this means, I may look for ways to advertise to drive the traffic.
Just to make up an example, lets say I owned widgets.tel (i dont). if the average order of widgets for company x is $100, and they find on average that they convert 2% of leads into sales, it means every lead is worth $2. Now, based on the example I could negotiate a rate, lets say $.50 per qualified lead, in which case I'm offering them a 400% ROI. (this is just made up for the sake of example).
My trick will be to discover my own conversion rate - how many of the visitors to my .tel will click through to the company, and how much do I need to spend in advertising per visitor to make a profit.
This is just one line of thinking but I dont see that its rocket science. of course it is more of a business model, not for lazy domainers. It may take some ingenuity and forward thinking but I don't see why it cant be done.
now the hope is that .tel will optimize well in which case generic terms will generate natural search traffic, and, that .tel will ultimately be adopted to the level that it will even get type-in traffic from people on mobile devices. In that case, your ROI is unlimited because you pay nothing for this traffic. That's the same power that premium .coms currently wield and why a business will pay big bucks for toys.com, loans.com, etc.
This remains to be seen, but at this point I think all bets are on as to how anyone will look to make .tel profitable, and as long as the medium itself works, people with enough gumption will find ways of leveraging it, regardless of the carping that "you cant build a website on it"
now, put that in your blog and smoke it :D