looks like you have a slow card reader. here's a substantially more
comprehensive test with speeds *much* faster than what you got:
<
http://www.robgalbraith.com/bins/no_nav.asp?cid=6007-8471>
There's no evidence of this yet. All his cards are quite
old and unrated (for any reasonable purpose of rating, what
real use is there when it's rated for a very low speed?,
"4X" was a quite low speed, today's "unrated" new-stock
cards generally achieve closer to 40X read with an optimal
reader.
The card reader could still be a bottleneck, though of the
few I have, none (assuming USB2 era not USB1) bottleneck
below about 12MB/s. They will tend to bottleneck the
faster new cards or from transfer of many smaller files.
Rob Galbraith's tests were of faster cards, while Joe was
showing what's possible with quite old and/or low-end cards.
To the OP, if you're interested in peak CF performance than
seek a modern generation CF3 or CF4 spec'd card (merely
having it state "CF spec" is not enough), generally rated at
150X to 266X, and use a CF-IDE adapter instead of USB. With
a modern 266X rated card running in UDMA mode from such an
adapter you should see up to (per your test, actual rate
depends on use) about 35-40MB/s read speed and a little over
20MB/s write.
Shopping online is probably a better bet than going
mail-order. For example in 2GB size,
http://www.newegg.com/Product/Product.aspx?Item=N82E16820211177
http://www.newegg.com/Product/Product.aspx?Item=N82E16820208296