There are basically three logs on the system:

Log:

• for short, textual data
• in-memory ringbuffer, fast
• ephemeral (you'll lose it on a crash, or the ringbuffer scrolls)
• intended for app developers

EventLog is:

• for short, binary data
• in-memory ringbuffer, fast
• ephemeral (you'll lose it on a crash, or the ringbuffer scrolls)
• intended for platform developers to collect statistics

DropBox:

• for long text or binary data
• persistent, written to disk
• kinda slow (disk)
• meant for platform developers too, mostly to collect crashes & large statistics
• subject to limits, deleted by tag if a tag's count and/or size get too large

DropBox is what we used during development to capture all the StrictMode violations in Gingerbread.

You can use DropBox for one-off debugging, but it's not really recommended. It's definitely not recommended as a way to share data between apps. It's not reliable enough, and you can't put permissions on the data. You should just use a shared userid and use the normal filesystem with appropriate permissions.