Currently, items selected in a Multi-Datasource field output in your layout in the order of their ID's.
You CAN write about 30 lines of liquid to control the order in which they appear, but most people can't do that, and you have to drop it into each place you're gonna do it. Not great.
Wouldn't it be great to have a param in the datasource tag something like "sort_order" where you could designate "selected". Like this below (see end of tag).
{% assign item_ids = this['Content Blurbs'] | join: ',' -%}
{% include 'webapp', id: '17', item_ids: item_ids, layout: 'default', datasource: 'true', sort_order:'selected/id/asc/dsc' -%}
This would output those items in the order they were selected in the Admin.
Bonus points: Allow for drag/drop re-ordering of items in the admin (but very much a nice to have).