Infinity used the EMIT ribbon tweeters for a long time, and I think they were designed before Harman acquired the company. I've heard Infinity's reference systems before, and their original Kappa line up. Those were excellent speakers, and I recall that the EMIT tweeter sounded great.

From what I've read about the EMIT tweeters, they had high failure rates, were expensive to produce, could not go especially loud, and were more difficult to drive than other tweeters. All that and more probably spelled the end for the EMIT. I'm trying to recall the company (Legacy Audio?), but at least one high end company right now still uses ribbon tweeters.