Personally I would also add,
1. If there is no demo for it.
2. If your weren't going to buy the game to begin with (and if you happened to really like it, you must)
Especially with these economic times. Theres no excuse not to have a demo, unless you think you're game sucks.
EDIT: Just watched the EXTRA CREDITS you mentioned. I still believe if a company doesn't release demo they're being a dick. I shouldn't have to write an email, it should be second nature. If you don't care enough about your product to give a player a 5 minute why should I bother paying for it legally before I decide if I want to buy it?
Heres a story, theres and Indy game maker named Adam Ryland (www.GreyDogSoftware.com) that makes a text based pro-wrestling sim game. When that games first edition (2004) demo came out, I decided to be a dick and fiddle with my PC until i got it to the point that I could play past the 48 hour trial period. Fact is, even though I had the full power then to play it for the next 1,000 years via my work around I ended up paying for it anyway because the game gave me that much enjoyment. In fact I ended up buying it well within that trial period (within 5 hours actually).
Just treat your customers right and offer a demo. NO ONE, let alone me, SHOULD BE HAVING TO SAY THIS.
ONE MORE THING- If you're a dirty pirate, at least have the morality to be able to say you are knowingly doing something wrong. More or less, we do all do it, it makes one slightly less in the wrong if you can at least acknowledge your knowingly doing something wrong.