Bitcoin Forum

There are at least 614 known altcoins. (http://coinmarketcap.com/all/views/all/) To keep an altcoin alive and tradeable, there must be a few miners and a blockchain. For how many of those altcoins has the infrastructure died?  Voyacoin, for example, was launched in February 2015 and was dead by May. (https://bitcointalk.org/index.php?topic=963475.0;all)

Market cap above $1B - 1 coin.
Market cap above $100M - 2 coins
Market cap above $10M - 8 coins.
Market cap above $1M - 32 coins.
Market cab below $1M - 572 coins.

Most of the ones below $1M have no market. But are their blockchains still live? Or did they stop paying their blockchain hosting bill. (https://bitcointalk.org/index.php?topic=1064635.msg11410407#msg11410407)

Some of them are still active and others are gone.
If you look at your example, voyacoin, according to coinmarketcaps, they are receiving trade data from C-Cex.
Here is a link: https://c-cex.com/?p=voya-btc (https://c-cex.com/?p=voya-btc)
So even though the blockchain reader is gone (not being paid for or whatever), it is still being traded on that exchange.
As long as one single miner is still mining the coin, there is a blockchain, but there might not be a blockchain reader around anymore.

In the past, when I traded altcoins (which I was very unsuccessful at), altcoins would die off everyday.
Exchanges would usually advise the users that a altcoin's blockchain is dead (hard forks or no miners) and freeze the trades, till it was fixed.
If it was fixed. Many altcoins are scams/pump&dumps/etc.

If the infrastructure for a coin is totally dead, it is usually de-listed, especially on coinmarketcap.
So if you see 614 altcoins currently, it is possible they are still active in some sort of way. But ultimately are slowly dieing.

Edit: spelling

You should exclude coins like Ripple and Stellar, they don't need miners to keep them alive, also due to 'premine' and the way they are distributed.

This list is better for this kind of analysis: http://coinmarketcap.com/currencies/views/filter-non-mineable-and-premined/

Somewhere over on the Altcoin board is a thread with a name something like "Necrocomicon" or somesuch that attempted to keep track of dead coins. Suffice to say there are a lot of them now, and many premature obituaries as well. Some coins may have a valid niche in the long run even with a small market cap, so don't write them all off. (Humble little Piggycoin being a favorite of mine and a case in point.)

There have been at least 2250 known altcoins (a handful unlaunched). There's an overdue update of details of ~100 recently-launched alts but you can get an idea of the range from a text-only list of names/symbols: https://minkiz.co/coin/name/ or you can thrash your browser with the full display which includes a best guess at status of listed, defunct or extant (neither of the foregoing). Some of the listed coins have been subsequently delisted: https://minkiz.co/coin/

The raw data (in the form of an RDF graph) is available on https://github.com/DOACC/individuals (https://github.com/DOACC/individuals), apologies in advance for the lack of documentation which is complete but needs updating with the latest data.


As an idle experiment, I'm keeping a few (those with <5 nodes) blockchains on life support: https://minkiz.co/acme (https://minkiz.co/acme), exactly as you describe.

Cheers

Graham