Depending on who you ask and which technical details you omit or include: * Quadratic scaling in signature checking * Increased storage requirements for full

Depending on who you ask and which technical details you omit or include: * Quadratic scaling in signature checking * Increased storage requirements for full node operation * Higher risk of mining empty block and/or creating minor fork blockchain * Centralized mining due to increased bandwidth requirements for mining nodes * Low/unknown support for big blocks among non-mining nodes At this point there are also important non-technical arguments: * Creating a precedence for further block size increments or hard forks * Giving in to vocal minority/"them" * Yielding some control of reference implementation * Pride