> I wonder how my day-to-day activities would change if I knew I was constantly eating away at my monthly limit
I've been spending the past 2 weeks at my parent's house in Australia, they live an hour from the nearest village and 2 hours from the nearest city. The only internet options are dialup, satellite or 3G. The 3G is surprisingly fast (6 MBps), but it's $60 for 4 GB.
I've been watching my usage, installed Little Snitch to disable all kinds of background activity like auto-updating. Most of my online time has been browsing HN, Reddit, IMing,, Facebook, Twitter, email, a couple Skype calls. Have watched a grand total of 2 YouTube videos.
I've still burned through 5 GB in 2.5 weeks. I don't even know how, aside from things when OS X spent 100 MB attempting to download the certificate revocation list, and Mail.app continually redownloading all my spam from Gmail.