Stephen Few's recent post titled Logarithmic Confusion contains a succinct description of linear vs. logarithmic scales:
units along a logarithmic scale increase by rate (e.g., ten times the previous value for a log base 10 scale or two times the previous value for a log base 2 scale), not by amount
For whatever reason, that description resonates with me. I like it better than what's on wikipedia.
The entire post is a worth reading. The gist is someone with a keen eye (Few) suspected a particular chart fit a pleasing narrative a little too well.