If you've tried to import a Drupal database dump with the cache table data still intact, you've probably at one point or another run into a "max_allowed_packet" error coming from MySQL. An easy way to address this is to increase the setting in my.cnf.
About a year ago I hit this issue, and came across this helpful blog post that explained how to copy one of the default my-XXX.cnf files into MAMP. I thought it was real cute how these files talk about servers with 64M-128M of RAM as being "medium" so I copied my-large.cnf or something in, tweaked the setting, and went on with my day.
Lately though, I've been getting out of disk space messages, which I've always found puzzling, since 99.9% of what I do on this machine is Drupal. And hey, I know jQuery UI is pretty massive, and I have a few Drupal 7 checkouts laying around, but what the heck? :P I started deleting things like old VMs I wasn't using anymore. But finally today I was down to about 200MB (?!?).
Little did I know, that if you copy in there anything other than my-small.cnf, this seemingly innocuous line is uncommented:
This turns on "binary logging" which means that MySQL will proceed to "helpfully" log every. single. insert/update/delete/create/etc. query you do. This is wonderful if you're running your own MySQL master/slave replication set-up, but not very useful if you're on a laptop running MAMP. :P
After taking a quick spin with Disk Inventory X, lo and behold I had accumulated 58 GB (!) of these mysql.bin.29837923 log files over the course of the past year.
The good news is that my laptop is screaming fast now. ;) But... yeah. Watch your my.cnf settings, folks! :)