I use del.icio.us for bookmarking and have a number of tags as Firefox live bookmarks. E.g:
http://del.icio.us/rss/sekhonp/shopping
Recently I found that each tag was only displaying the last 15 entries, it looks like del.icio.us have reduced the default size for rss feeds. To get round this just change the live bookmark url to include "?count=maxNumberOfEntries", e.g:
http://del.icio.us/rss/sekhonp/shopping?count=30