My understanding of the sponsorship system is that the company has to prove that they're unable to hire someone with your skill-set locally. To do this they have to prove you have a specialized skill-set, which means either a university degree, or 12 years industry experience.

I was approached by Facebook a while ago but nothing came of it as I didn't have a degree, it would be too hard for them to get me a visa.

I'm not too concerned with increased earning potential, or ability to actually get jobs. I earn towards the upper end of the pay spectrum for my field in New Zealand, and I've never had trouble getting interviews. I'm more concerned that I'm going to have issues moving into leadership positions and the like. Perhaps I'd have more trouble overseas though.