This is indeed an idiom. More precisely, it's a corruption of one. It comes from the phrase "drop of a hat":
Bob is always angry. He's willing to start a fight at the drop of a hat.
There's a question at ELU relating to the origin of this phrase. The general opinion is that it comes from the (supposed) Old West practice of an arbitrator dropping a hat to the ground to signal the beginning of a fight.
*How does this relate to the phrase in question? Consider message boards or chat channels. In these communication media, when someone posts something radically opinionated, it tends to start a strongly heated discussion, or even a fight. Someone "dropping an opinion" on the channel, therefore, is someone attempting to instigate.
In the given context, of course, the phrase seems to be used positively, in the same sense as:
Bob is a great guy. He's always willing to help out at the drop of a hat.
"Drop of an opinion" is not standard English, so be aware that use of the phrase could lead to confusion. "Drop of a hat" would be clearly understood by most native English speakers.
**This paragraph is original research*.
Blame, pin upon, hold accountable
These are the nearest meanings.
Note: Finding many examples of this usage on the web but not authentic source as yet, still looking, will edit as soon as I find one.)
It pegs the responsibility entirely on some vague and nebulous “them”.
The new status of the case, in effect, pegs the responsibility for commissioning the crime on a single culprit.
Best Answer
It's recently (AFAIK) become common to refer to the act of releasing a new product release as "dropping", particularly when the product is something that might be eagerly awaited by customers.
This usage seems to have originated in the music industry. For example, you might ask "When will Drake's new album drop?".
Some online sources also show a transitive usage, like, "When will Drake drop his new album?", but I don't recall actually hearing it used this way in real life.
So this quote is talking about the release of a new shoe design.