You might do screenscraping of any online database that posts prices.
Screenscraping refers to extracting information from web pages on the
web. Unless the authors permit reuse, you are violating copyright by
doing that. I got in trouble by screenscraping foreign exchange rates
off the Oanda site. Even material that looks fair game for reuse, e.g.
prices, is not necessarily so. It is a legal minefield. It seems that
manually extracting information is considered less sinful that using a
program to do it, but you can still get in trouble.
Even if you screen-scrape for non-commercial purposes, even if you
don't repost the data, and even if you don't put much load on their
server, they can still get irate, block you and send lawyer letters. I
think the main reason is they put up their site primarily to serve
ads, (the data offered are just bait), and you obviously are not
reading the ads if you are screenscraping
see
http://mindprod.com/jgloss/screenscraping.html
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