Alice first meets the Red Queen. In the middle of the conversation the Queen grabs Alice's hand and they run as fast as they can for a long time but never move. After they stop under the same tree where they started, part of the dialog goes as:
'Well, in our country,' said Alice, still panting a little, 'you'd generally get to somewhere else — if you ran very fast for a long time, as we've been doing.'
'A slow sort of country!' said the Queen. 'Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!'
The moral of the story for SEO: if you want to maintain your search engine rankings, if you want to stay where you are, start running. Hard and fast.