Low quality logo.
The image is a .GIF file, meaning there is only one alpha.
A Portable Networks Graphic (PNG), the normal transparent logo here on UserLogos.org, allows for semi-transparent pixels, so the pixels aren't necessarily a solid color or a transparent color.
They can be semi-transparent, so the logo flows smoothly from logo to transparency.
Look at my logos, and you'll be able to tell the difference immediately. (Not to say my logos are the best on the site, it's just I use PNGs.)
All in all, -1.