Imagine your car. It is snowing outside and it is above freezing. The snow hits your car and it melts on contact. You swipe your hand and it's just water. Would you still deice?

ok to attempt to pull this back to the original question without a PhD involved.... Why get type 1 and 4 when it's just frost or maybe a very light snow? Because many hub stations are now diluting the type 1 so thin that it's mandatory to put type 4 on even if there is no active precipitation. It's called a blended station and gives no option to just use type 1 because the type 1 is so diluted it doesn't meet the minimum freeze spread... the bean counters say this method is cheaper... I don't give two hoots as I keep breaking guarantee on reserve and this just adds to it. Most block times are now accounting for this in winter, and the few that don't mean the bean counters had best planned for the fuel burn to try to make up that extra time deicing.

Drops mike and grabs a glass of Bourbon and a cigar

No kidding. Why on earth is this even a six page discussion?

I can't believe no one touched on the CYA aspect of things. In this day and age where every passenger is an undercover reporter, can you imagine the sensationalistic headline following some hero passenger posting a YouTube video of his "dangerous" take off with some minuscule amount of snow on top of the wing?

De/anti-icing is CYA, it keeps the "A" alive. This job isn't about pushing the limits/envelope, it's about doing your job and going home to your family and friends. If it costs the company a little more to operate in in adverse WX conditions, I am OK with that.....
Flaps up, flaps down taxi, it's just a procedural change. Our SOP was just changed for no good reason, for the worse.

I wasn't trying to imply that it's a good idea to skip out on de-icing, quite the opposite. The cost numbers don't even cross my mind during the decision making process. If it's gotta be done, it's gotta be done. If there's any precip falling, I get the type 4. This business is full of Monday morning quarterbacks out looking for their 15 minutes. I will always do my damndest to not ever let anyone get their 15 minutes at my expense.

Temp drops one or two degrees while in the line-up and now it's frozen on your wing. Crap happens. Not very often but our predecessors proved that if you play the odds with ice eventually it will go wrong.

If it's coming down or reported get at least type I if you can go within the HOT.

As others said if a PAX sends cell phone video of snow coming down to the FAA, you didn't de-ice, and the METAR says -SN you'll have an uphill battle to avoid a violation.

CYA...both your regulatory and physical butt.

I'm just going to leave this here........

What Ryanair crew member tells passengers when she's explaining delays | Daily Mail Online

Absolutely. Wet, heavy, sticky snow. If ever any type of snow would adhere to the airframe it's wet stuff right around the freezing point.

Not to mention, where did the plane come from? Was it just brought in from a six hour transcon that has cold soaked every square inch of it? Is this an early morning departure where the sun has just come up raising the temp quickly after sitting overnight with cold fuel in it? So many variables, there is a reason why ANY frozen precip, or any precip with temps below freezing, and your company wants you to get sprayed, and so does the FAA. Why overthink this?

My company makes such a big deal about this that if the FAA is calling snow on the field but it's no longer snowing the company gives you two options, either ask for and receive a special observation or call DX and mark it on record over a recorded line that there is no snow on the field. It's a huge deal.

In your example, do I think it's a safety issue? No not really. The airplane will be fine most likely. We tend to way overdo it now in regards to de/anti icing, I agree.

See, it blows right off.