Courtesy of @Haplo I was inspired to finally sit down and crunch the numbers for something I’ve believed for a while but had no hard proof. Et voilà! 
Thesis: Using reversed cards in a Tarot spread means that, probabilistically speaking, you are more likely to foretell a negative outcome/answer for your question.
Methodology:
Using the Biddy Tarot definitions (Learn the Tarot Card Meanings | Biddy Tarot) I’m categorizing a card (whether in the reversed or upright position) as having a negative meaning if the number of clearly positive terms in its definition is greater than the number of clearly negative terms. I did not count those that were on the fence; i.e., the definitions that had equal numbers of positive and negative words.
Results:
17 / 22 of reversed Major Arcana have negative meanings compared to 3 / 22 upright Major Arcana.
7 / 14 of reversed Cups have negative meanings compared to 2 / 14 upright Cups.
7 / 14 of reversed Swords have negative meanings compared to 7 / 14 upright Swords.
10 / 14 of reversed Pentacles have negative meanings compared to 1 / 14 upright Pentacles.
8 / 14 of reversed Wands have negative meanings compared to 1 / 14 upright Wands.
So we have (17 + 7 + 7 + 10 + 8) = 49 reversed cards with overwhelmingly negative meanings compared to (3 + 2 + 7 + 1 + 1) = 14 upright cards that have overwhelmingly negative meanings.
Therefore, assuming the probability of randomly pulling a reversed card vs. an upright card from a shuffled deck is (1 / 2), the probability of getting a negative card allowing reversed meanings is (1 / 2) * (49 / 78) + (1 / 2) * (14 / 78) = (0.3141 + 0.0897) = 0.4038 or 40.38%.
vs.
The probability of randomly pulling a negative card from the deck using only upright meanings is (14 / 78) = 0.1795 = 17.95%.
In other words, you are (40.38% - 17.95%) = 22.43% more likely to pull a negative card by allowing reversed cards in your Tarot spread.
Discussion:
This seems to confirm my hypothesis (please tell me if I’ve made any mistakes with the math!). Of course I am not considering the other big factor in Tarot readings which is the use of intuition to determine a specific card’s meaning outside of the standard definition, nor am I taking into account the fact that the meaning of various cards changes depending on their context and placement within the reading as a whole, but going from the numbers alone it seems like allowing reversed meanings does make it more likely you will get “negative” cards.
The question is, now, how does the mechanistic probability of selecting a particular card interact with the synchronicity of “randomly” selecting a card that matches up perfectly to answer your question? In other words, how does Randomness/Chance mesh with Predetermination/Fate?
I’ll get back to y’all on this as soon as I figure out all the other unsolved philosophical and spiritual problems that torment me. 
I used to think the brain was the most important organ. Then I thought, look what’s telling me that.
–Emo Philips