I happen to forget links sometimes, that is true. I add them then once someone mentions it or I discover it by accident.
Windows 7 article: Got tipped of by a reader with a direct link to the forum.
Last.fm: My feed reader has currently RSS feeds of about 500 sites and portals including blogs from many popular websites. Guess how I found out about it ?
Read Email: Spy Pig was first mentioned, IIRC, on Go2Web20.net and not on Digital Inspiration. Did Digital Inspiration mention their source ? No they did not. Did you post the same accusations there ? No you did not. I do not like linking to Go2Web20.net because if you open that website you see that there are no direct sites for each service that they write about, just a huge page with logos.
I'm not saying that I'm perfect and I tend to forgot links from time to time but I try my best to cite my sources. That's all I have to say about this. But continue if you like, would be a nice blog idea I guess

Mouser it does not really make a huge difference if I mention a source in the first part (that hits the frontpage) or at the end of the article because articles are mostly accessed directly anyway.