The best practices/setup doc 1054431.1 doesn't mention anything about compression for the tablespace holding the dbfs data. Understanding of course a performance penalty, has anything been written about a desirable configuration settings for this?
Technically DBFS is available for non-Exadata as well, so it's included in the Oracle license itself, nothing related to Exadata.
The compression that is used by DBFS is not OLTP or Direct Path compression, which you can set at the tablespace level, it is Secure File compression. Looking at the docs,
it appears that Secure File compression and deduplication are part of the Oracle Advanced Compression Option, but I'm not 100% sure how that works with DBFS. Let me see what I can find there...
But using compression anywhere is about trade offs, it makes sense and adds benefits in some cases and in others the tradeoffs are not beneficial. Depends on your specific case.
A point to consider here is what are you, or will be, using dbfs for. If it is to store files before loading them into the database, then advantages of using compression or deduplication... will depend on these files. If they are gzipped, or for example some kind of images, ... then securefile compression will not help. But if the files are not compressed, it may help a lot. But, as Greg said, it is more function of what you're doing with them, and the trrade offs you can make between cpu power used to comrpess/decompress, and space usage.