1) If you download an application that seems to be "tiny" in comparision to what it should really be (ie., 100K opposed to 100Mbyte), then one would suspect ome of the following:

1a) Its an unrelated file purposedly renamed to what you were seeking.

1b) Its a mallicious application. Someone is hoping you'll execute that file, with the purpose of causing harm to your system or install, say, a trojan.

1c) Your Gnutella client thought it had the entire file, while in fact it didn't download everything

2) Your results may not "mac-friendly" if you didn't include specific keywords related to your OS. However, some files can be accessed on various operating systems - sit files are among those.

3) Generally, you would want to compress files to make it easier for others to download it. However, there are some file formats where compression can actually make it larger than the original - MP3 or OGG files for example, which are already compressed in standard form.