Another interesting search engine is being shuttered. Hshtags at https://hshtags.com/ is closing down as of September 12th, which isn't exactly a long time away. The engine has been around for 3 years and was one of my favourites to point people towards when they wanted to search social media based material. It returned results in a nice 'tile' format and the coverage was wide, with Twitter, Facebook, G+, Instagram, Flickr etc all being searched. The only reason that they've given for the closure is "over time, the upkeep outweighed our passion." I think the lesson that we can take from that is that if an engine doesn't have a good money making structure behind it, naturally it will struggle.
What are the alternatives?
There are several alternative engines that might fill in the gap, and Hshtags have suggested the following:
Tagboard which is an engine that I've used and it's worth looking at.
Tint at http://www.tintup.com/ is a commercial product, with rates starting at $300, so I don't think many of us are going to be looking in their direction
Brandwatch at https://www.brandwatch.com/ is another priced product, and you have to request a demo as well, so for most librarians, once again that's not going to be appropriate.
Talkwalker at http://www.talkwalker.com/ is another in the same vein.
Mention at https://mention.com/ is a great tool and one that I use myself. It's also free, which makes a change!
Hashtags is the other obvious engine to look at, and you can find it at https://www.hashtags.org/ and it's where I'd suggest that you start exploring first.