By this logic no two companies can ever join in a beneficial partnership because every other company in a similar field isn't involved. Unless you're definition of 'harming' a competitor is doing a better job of marketing yourself to customers, I still can't really see the harm being done to tinyindiesite?
You still pay for your music service, you just don't get it applied to your data cap at a particular phone company. Yes, that allows Pandora users on T-Mobile to get more use of their phones/music but it doesn't prevent tinymobilesite from operating on T-mobile through any other ISP.
For the record, all the talk of t-mobile is moot anyway since any music service can register with them to be used without data restrictions. As someone else pointed out, a person managed to register his home computer to be his personal streaming service.
My point is that even if that weren't the case, it's not up to T-Mobile or Pandora to help tinyindiesite get a leg up. As long as T-Mobile isn't the only possible ISP through which tinyindiesite can operate and they aren't artificially affecting transfer speeds to affect tiny's performance then it's up to tiny to make their service competitive either through pricing, quality or making their own deals. Having the government step in to make things fair rarely if ever works out for the market and it's consumers in the long run. The government has some responsibility to provide protections (anti-dumping practices and such) but in general government involvement causes more problems than it solves. In fact there's a current Supreme Court case about raisins in which the government, to make things fair, want to confiscate 1 million pounds of a growers product, without any compensation, or have them pay $700k in fines, so that they (the government) can properly manipulate the raisin market. It's very similar to the Canadian Wheat Board which routinely forced farmers to let their crops rot instead of selling them for prices they (the government agency) deemed appropriate.