I believe he means that if you have a constant rate of 6 blocks/hour and a fixed number of max-transaction-per-block, when the number of transactions is going up, they eventually go above the "bandwidth" limit (which is: 6 * max-tx-in-block / hour) and instead of being mined at the time when they are announced, they are getting queued, to be mined later...
Which is exactly what I have been observing for the last few weeks - even transaction with a proper fee needed like hours to be mined.
And this is very bad.
Bitcoin really needs to start handling bigger blocks - otherwise soon our transactions will need ages to get confirmed.
The network will just jam, if we stay at the old limit.
I don't believe the design specs for bitcoin will allow this, it just isn't possible to scale it without a complete redesign of how the internals work. Kind of the reason this problem has shown up now while other theoretical problems will come in the near future.
