Great Question! The super small files are just shortcuts to the internet site. You get an icon for a specific website. Some people like this, but bookmarks can do the exact same thing.
When trying to see if an app is "safe", I usually do the following:
1. Check user comments --- if tons of people are saying bad things about the app, then its probably no good.
2. See if there is an official website --- like "do they sell this thing" and "does it exist outside of GetJar"
3. Use common sense.
4. Ask the community in the comments (Lots of great commentators on the "Install Non-Virgin Mobile....." hub that are ready and willing to help)
5. See if you can get the same app from a trusted source if you think it looks sorta "sketch". Howard Forums, my Mediafire Folder, the Willie Links, VMTouch.com, etc.
In the end, there is always some risk.