The Steem blockchain is is now capable of supporting virtually any kind of blockchain application imaginable. More importantly, with the STEEM API now fully deployed you do not require prior permission to commence development and you will have access to STEEM's rapidly expanding userbase. In fact, recently I read a really great article about the top ten reasons to develop applications for the STEEM blockchain by The Monetary Few. The ten reasons include:
1) Most transactions
2) No transaction fees
3) 20 successful hard forks
4) steemit.com is being used
5) The attention economy
6) Two ways to measure importance
7) The Steem community feature is coming
8) Delegated Proof of Stake
9) EOS.io - A new smart contract platform
10) Get paid for your work
You can review the full article at https://www.pmncoins.com/index.php?option=com_k2&view=item&id=318, an instructional video along with some useful programming resources and API consumption tips.
Additional tips can be found at https://steemit.com/steem/@furion/developers-guide-to-steem-s-blockchain