I wasn't following it closely (and was a little disgusted) but as I recall, all lukedashjr did was mine for a while then quite and it had a devastating impact on whatever coin it was.  Hell, the same thing could happen to Bitcoin without any attack if the price drops steeply or suddenly (but that could never happen, right?) and/or a few large clusters were molested.  I'll call this an 'Invisible hand of Adam Smith lukedashjr Attack.'  Maybe the adjustment algorithms have been patched up to preclude this, but I doubt it...such things occurring proactively seem rare in Bitcoinland.

Second, even with an "infinite" block-size, there are still practical limits to the size of blocks. For example, my full node (with idle token hash-power) is currently set to broadcast 500kB blocks. The reason is that my (ADSL) Bandwidth is limited to 5Mbps up. If I want to send a newly found block to 16 hosts at once, we are talking a delay of about 12.8 Seconds. With a 600 second block-time, that corresponds to an orphan rate of at least 2.1% (one hop). If I had a 1Gbps connection, and wanted to limit my orphan rate to 5%: 600x.05=30 seconds. 1Gbps*30s/(say)64 connections*8bits/byte=58.6MB Block-size (again assuming one hop). At about 300 bytes per transaction (many transactions are larger), that works out to about 195 thousand transactions per block.

In other words, people will naturally stop using Bitcoin to buy snacks/coffee.