EOS Meet up - What is a Block Producer??
An EOS Block Producer is the authority and curator of the EOS network. [undefined] Within the DPoS system, Block Producers run the underlying network layer to process all transactions on EOS. [undefined] [undefined] There will be a total of 21 block producers along with another 100 Back-up nodes overlooking the activities of the 21. "Healthy" candidates for the Block Producing role on the EOS network must fulfill a list of criteria and attributes in order to be considered for a vote. [undefined] [undefined]
What Are The Qualities Of A Great EOS Block Producer?
The activities performed by Block Producers should be covered by EOS as each BP runs the producer plugin.
The software, DPoS, is the system that EOS will operate on.
Block Producers replace the concept of “miners” as the custodians of the network, running the underlying network layer to process all transactions.
For DPoS, there is no expensive, wasteful proof of work that is paid for through inflation and new coin release such as Bitcoin and Ethereum (currently).
On EOS, Block Producers service the community and the network.
BPs must implement arbitration decisions when instructed and make the hard investments to scale as required.
Block Producers also act as CEOs in a traditional company as they must keep everything internal and in control.
They must also communicate with other BPs and can also campaign to get elected as a BP.
A healthy Block Producer on EOS.
All block producers will have a full copy of all of the files in storage so when a file is uploaded to a block producer, synchronization must occur to the file within a reasonable time.
Synchronisation is a one time event, as soon as a transaction is detected then all block producers should start download, if they later decide to delete it then and will refuse to serve this file, even if it is still available via IPFS.
Files in storage can optionally be served from a https server listening on a common domain, or the domain name of the customer.
Each custom domain name should have a SSL certificate automatically generated from letsencrypt.
Accounting for bandwidth should also be done, bandwidth costs could be receiver pays or uploader pays.
The https proxy will need to be connected to the blockchain to verify permissions and accounting.
Voting on issues such as freezing accounts, replacing contract code, deciding on new storage limits etc. 
In addition, BPs must also perform the following:
Following the constitution
Account freezing, misbehaving contracts
Take-down notices of files
Hard and soft forks, fees (account creation), parameters (blocksize, rate-limited capacity) [undefined]
According to Thomas B Cox, a "healthy" Block Producer should have the following:
Demonstrate a track record of reliable block production, if not new.
Possess data center assets of "good enough" quality -- as independently certified
Participates in BP discussions and gets a positive rating from other BPs
community-enhancing activities that get a positive rating from watchdogs [undefined]