Oh, around 2790 ELO or thereabouts...
At what level....

Depends on rating, place, tournament standing, prize fund, time control, mood, whether opponent is experimenting with an opening or it is his pet opening, hangover, how much sleep he had in the night before, time spent awake, amount of cups of coffee imbibed, alcohol promillage, how many games were played before this one, how blunderful they were, etc. etc.
So yes, they'll fall for it every now and then.

Do players not fall for opening traps any more?
It always surprises me when 1800 or 1900 players fall for elementary well known traps.
Well, the accepted "wisdom" is that you don't need to study openings if you are rated under 2000. I know I haven't really studied any opening traps.
The same level you're good enough to never miss a two move tactical shot...
Never
Hey i'm sure kramnik never misses...
oh wait

Zapata - Anand ended in six moves:
Amazing! It's a very good puzzle to figure out why Anand resigned. If you can do so, you have worked it out as soon as he did.

Anand's comment:
. . . So I decided to go for Plan B, which was to resign and then get out of the hall as quickly as possible, so that nobody would notice. This worked successfully - for many days people thought I had agreed to a short draw with Alonso - a very short draw.
"A very short draw."
It's games like this that make my terrible blunders easier to accept.

The Grob, 1.g4, while technically doesn't contain a trapping line, allows White to get a piece for a pawn up with careless play, which happens not infrequently.

Anand's comment:
. . . So I decided to go for Plan B, which was to resign and then get out of the hall as quickly as possible, so that nobody would notice. This worked successfully - for many days people thought I had agreed to a short draw with Alonso - a very short draw.
"A very short draw."
It's games like this that make my terrible blunders easier to accept.
Indeed lol
Do players not fall for opening traps any more?
It always surprises me when 1800 or 1900 players fall for elementary well known traps.