re: slowing down transactions
This could actually have benefits if done right. Consider a stock market where buy and sell bids are paired at the end of the day so that the highest buy bid would be paired for the lowest sell bid at (buy+sell)/2, the pair is removed from the pool and this goes on until either buy or sell bids are exhausted. This would eliminate short term (<= 1 day) trading which destabilizes the market* and leaches money to the short term traders from the rest of the market for no discernible general benefit**. There is no real reason to run the market on a shorter timescale than a day (never mind a microsecond one): it is, after all, closed down during nights and weekends***.
* potentially resulting the rest of the economy going pear-shaped for no good reason (screwing up even those who don't participate in the market)
** except, allegedly, providing liquidity, which this scheme would do as well if not better
*** actually 1-3 times / week seems enough and would result in more stability and effective liquidity (for a stock or bond market, forex might need a shorter timescale (a couple of times / day, maybe))