OK, I missed that fact that you were asking an Architecture question. Sorry.
I'm not sure how the design avoids a junction table if the cardinality of the relationship is many-to-many. I've seen the use of bitmaps to do this, but I can't see how guids would be used in this scenario. The bitmap field is stored as an integer, where each bit represents a fact or entity. It can increase performance for intersections with relatively small domains.