Amazon.com is a very effective logo. Even though they are a fairly new company (only since shortly after the conception of internet shopping, which wasn't too long ago), they have established a recognizable logo. A sans-serif font is used because as an internet company, they are very modern. Amazon is bolded to stand out among the .com. The yellow is effective because its a bright color in contrast to the black. But the main feature that makes this logo most effective is because the arrow points from the A to the Z, to suggest that they have everything- "from a to z." It's very clever and extremely well executed.