topr8 - that's a good point.
We can't get get true high speed internet at home. We finally got satellite two weeks ago after getting an easement from a neighbor to put a dish on their property (no line of sight from ours), trenching, running conduit, etc. But I digress.
My wife has high-speed at work, and we had access to DSL at other locations.
Not true for most of our neighbors, and satellite dishes have been springing up like crazy in the last two years. Two years ago there were two people in the 'hood with satellite. Now I know of about ten (out of perhaps 25 full-time households).
Anyway, satellite still sucks (the latency is a killer and it bogs down horribly in the evenings).
The main issue is that sites with lots of little files can just seize up (Yahoo mail is almost better over 26Kb dialup).
So looking at a YSlow analysis is likely relevant. CSS sprites would be more important for a satellite user than, say, JPEG optimization in general.
And also, realize that many areas that can't get DSL can't because they, like us are on pair-gain systems, commonly used in rural areas to serve many homes off one copper pair. Most pair-gain systems can only handle 26Kbps on dialup. In fact, I have never lived someplace where I could get dialup at faster than 26Kbps. So if you see "dialup" and think "56K", you need to cut that in half again.
And a point I made previously (I think the last time Ogletree brought up something similar)...
I would guess the 40% is comprised of two groups: the poor and the rural. The poor are likely not spending a lot online anyway.
But as I've often said, if you're too far out to get DSL, you're likely too far out to get to the store easily. In our case, it's 2-2.5 hours to the nearest Target, Lowes, Home Depot, Wal-Mart, Best Buy, Borders, etc. It's 1 hour to the hardware store, auto parts store.
So if I need a new keyboard, for example, it's 4 hours in the car and $20 in gas.
Am I more or less likely to buy online that someone who lives in the city?
Am I more or less sensitive to shipping costs?
If the same keyboard actually costs an extra $5 online, plus an extra $10 in shipping, it's still often cheaper and easier for rural people to buy online and lots of these people are on slow connections and will become repeat customers.