Quite a significant amount of traffic to this blog comes from people looking for information about Facebook Scramble highscores, what the highest score is.
Its a difficult one, for each grid, it actually says what the highest possible score is, if you get every word thats in the grid. It even lists how many words there are for each length up to eight letters, and when you've finished playing, it lists every word too.
This one time I was playing a game against a girl with a huge vocabulary, she got around 350, I was mighty impressed. But on the same grid, I set my own personal best score of around 250. It was a high scoring grid, worth around 2500 points in total.
There's only one way to get a score anywhere near the maximum, and that is to cheat.
Wikipedia has some details about typing speeds, it says that average for a professional is 60 WPM and super ninjas can do 120 WPM. I'm guessing average word length is 4.2 letters per word, which together means you get around 6 or 8 keystrokes per second. Thats for professional typist, maybe transcribing stuff, rather than thinking about what they're typing, but lets ignore that minor detail.
The spread of letters in a grid means that around 5% of the score comes from three-letter words, 20% from four-letters, 25% from both five- and six-letter words and then the bell curve drifts back down for longer words.
For a grid worth 1000 points, in professional keystroke terms, its going to take 260 seconds to get every single word, which is a shame cos you only have 180 seconds, three minutes. Its not physically possible to get every word, you run out of time. If you start with high-value long words and then work down to the shorter words, you run out of time in the middle of the four letterers.
The human brain doesn't even work like that. It looks for shorter words than adds -s on the end and -er and -ers, -ing, -inger, -ingers. The human brain starts simple and goes complex when its looking for words in scramble, rather than starting long and going simple.
I ran the sums.
If your grid is worth 2500 points, its going to take around 600 seconds to type every word, if you're going as fast as your nimble fingers can go, ten minutes. You're going to run out of time in the middle of doing six-letter words.
I reckon with human typing speed limitations the highest score is around 1200, thats ignoring the way the human brain works and ignoring any kind of thinking about what you're typing.