We have been solving many of the issues of Google Moderator with http://www.sli.do. Even some Google offices have been using sli.do at their events instead of the moderator.
This is not really accurate, though i guess it depends on what you consider the smartphone era.
It was still a solid product, that just became a bit "old" as technology progressed. As mentioned in several comments here, better alternatives (incl sli.do) are now available.
Actually, we had a new mobile UI built in ~2010, and tested it at various conferences and in various other products.
The truth was the product wasn't going to do well outside of some niches, because the large content providers wanted something they could either control, or that was just more popular even if it wasn't a good fit (IE CNN/et al wanted facebook/twitter for their on-air shows, and were okay with hiring full time people to do curation)
So, yeah, mobile didn't really kill moderator, despite your claims.
I just heard some of our clients that were using Moderator before that they switched because of the mobile UI. Was it ever available for public?