If you think Topps is bad about issuing lots of parallels, you should take a look at the secret world of BBM issues. Most BBM pack-based sets have at least two tiers of insert sets. Team sets have foilboard and holofoilboard (my new word!) versions, with the latter being serial-numbered. Topical sets (such as the Historic Collection series) and the flagship series releases seem to usually have a couple of foil signature colors - 2013 BBM 2nd Version has at least silver, gold, holographic, and red. Information about the existence of these parallels is rarely made by BBM itself.
The real trick, though, is the multitude of promos and limited editions they issue to stores, events, and stadiums.
I picked these all up as I was getting my 2nd Version singles. Finding parallels and promo-issue parallels is both good and bad at the same time - I'm glad I've discovered cards that aren't really cataloged and I can show them to you, but at the same time it adds to my overall "burden" and cost of assembling my type collection.