Say I want to warehouse tick data for resale at a later date, what kinds of legal issues could I run into, or worry about? Do different data feeds have better contracts for this? Sorry if this is stupid.
Most data providers consider the information to be proprietary, which means that you would need an agreement to resell the data. Your data supplier, in turn, probably has an agreement with the exchange, so you could be looking at coming to an agreement with several parties. From your customer's point of view, it would probably be cheaper to deal directly with the source than with a middleman, assuming that they want to do things aboveboard.
I was thinking that about being the middle man. I just think there are people just starting into the blackbox arena that don't have immediate piles of data for testing. It would also be cool to setup a server with loads of data that someone could connect their blackbox to. The server then spits out tick-data directly to the blackbox. This could allow programmers to not have to focus on setting up databases, hooks, and things just to test their strategies. Maybe I am wrong in this thinking, though
The repective exchanges would have a problem with you, not so much the datafeed provider. For example, see: http://www.cmegroup.com/market-data/distributor/
Yeah, or undercut the exchange. The way illegal music downloads work on the internet, I'm surprised people don't push around market tick data archives. Ask NYSE what their monthly charge is for OpenBook Ultra. Unless you are cranking out profits like a mad-man, this stuff is out of the reach of retail traders. I tried to archive this stuff at work, and had around 400-500GB of intraday data -- when I wanted to get it out, I got shut down by firm administrators looking to make sure they were on the good side with the exchange. It's a tough game, man. I archive the e-signal ticks [shitty, I know], but that's the best I can do outside of a well-funded environment.
opentick.com used to do exactly that (for free). They closed down, and some speculate one of the reasons was they had frictions with the exchanges.
Many of the exchanges allow you to download free data with no restrictions. They can't later put restrictions on that data except by claiming copyright. And I believe that databases are exempted from copyright protections. So if you got your data for free off a web/ftp site, they probably can't stop you from doing anything with it. If you paid for your data, you'll have to read your customer agreement to see if you can redistribute it. It is somewhat ironic that if you pay for data you probably have fewer rights than if you just grab it for free. Alternatively, you could always move to a country that doesn't enforce US copyrights, and then do whatever you feel like doing.