The extremely unfriendly attitude of many of bitcoin developers to added services and higher-level protocols such as Counterparty and Mastercoin being built on top of Bitcoin is very worrying for the future relevance of Bitcoin itself versus other cryptocurrencies.
Services like Counterparty and Mastercoin are not simply altcoins. They add extra functionality to Bitcoin, such as trust-less distributed p2p cryptocurrency exchanges (Mt. Gox told us we need those!) as well as all kinds of financial instruments, including asset creation, dividend payments, and hedging.
With the recent release of Bitcoin version 0.9.0, the planned prune-able OP_RETURN transactions that Gavin Andresen announced back in October 2013 as designed to store 80 bytes of data on the blockchain were suddenly reduced to 40 bytes, against the interests of such higher-level protocols.
Can Bitcoin afford to stifle innovation in this way?
The fact is there are many competing cryptocurrencies in the game and that if innovation doesn't happen on top of Bitcoin first (or at least practically concurrently with other altcoins) then Bitcoin risks losing it's lead and maybe even fading away.
Read more: http://letstalkbitcoin.com/the-greatest-threat/ and discuss.