its called a photo proof. Most people send in low-res copies (normally watermarked though) to Magazines, Athletes, and Team Managers for possible sales. These are perfect for preview because they are small, quick, and give a good view on a computer which is only a limited size and resolution.
People expect to sell photos mostly for print, so when a company takes a photo that was taken and submitted for possible sale, the company/magazine/TM will ask for the high res images for specific uses, thats when contracts/usage is negotiated.
However the web only displays a limited amount of PPI, so a low res image- Is perfect for the web. You cant tell its small or low res because it displays so small.
The fact is most payment is negotiated by the amount of times someone will see the photo or it will be displayed. The grenade website probably gets a fair amount of traffic, and through most photo price quoting programs, I am sure the usage fee was more than a 2 digit number.
Everyone that is saying he should have ate his words and let it go "for business purposes" and the thats just the "cost of doing business" have no idea about the photographic trade, or the market for that matter. Every time a photographers work is given up for free, the overall market, and other photographers are hurt. In a trade that is quickly dying out, it is imperative that photographers and filmers work to ensure the value of their work, as well as others. I am sorry but "the cost of business" is not just giving out your product for free to anyone who uses it without asking.