Aggregator developers are discussing the subject on the RSS-AggDev mailing list.
I'll use this entry to keep a running tally of how RSS 2.0 implementors deal with the enclosure tag.
Aggregators: FeedDemon, GigaDial, and RSS Bandit look for no more than one enclosure; BottomFeeder, FeederReader, and NewsGator support multiple items.
Publishers: DasBlog and Radio UserLand produce one enclosure per item; WordPress and Blogware support multiple enclosures.
PyDS only produces one enclosure at most and only expects one enclosure at most.
Tucows' Blogware supports multiple enclosures.
We also have several about to be released projects that implement the spec similarly.
FeederReader supports downloading and playing multiple enclosures, manually and automatically.
Author, FeederReader - The Pocket PC RSS reader and podcatcher
Pereved! Hi all! Nice day! =)