How does merge replication work with SQL Server CE
SQL Server Compact has a built-in change tracking mechanism (similar to SQL Server Change Tracking), and when a database file is merge replicated, a number of system tables are added to the database, see http://blogs.msdn.com/b/sqlservercompact/archive/2007/04/18/merge-replication-system-tables.aspx - conflicts are only handled on ther server side. In addition to the tables mentioned in the blog post, some _sys columns are also added to each merge replicated table.