I've seen realtors ask for ID unless you're accompanied by another realtor (who would leave a card). Basically they want a record of people through the house in case something does happen. You could easily make a fake business card, of course... professional courtesy means a realtor seldom asks another for an id. But this would likely only work briefly in a given area once word got out.
That isn't how an open house works (at least in my experience buying a house in Los Angeles in 2018). They advertise the hours, put up a bunch of balloons, and anyone can walk in. They ask you to sign a sheet so they can contact you, but I never saw them make anyone sign it or request an ID. I visited maybe 30-50 houses doing open houses, and a good half of those weren't with our realtor (or they arrived well after we did).
I went to 50+ open houses in the 3 years pre-Covid (finally bought a place just before it started) and was never once asked for ID. They usually ask you to write down contact info on a sheet, which I do using intentionally impossible-to-read handwriting to avoid follow-up spam.
I bought my house in a raging micro bubble in the Bay Area and got the first one I made an offer on. Really just depends how much you care about getting a good deal. I did some math and figured it wasn’t worth the effort.
There's a lot of stuff that looks better online than in real life ;)
And we took quite a while to figure out what we really wanted (and we were comfortable living in the place we were in, so we didn't need to make a change...)
We only ever made three offers, two of them on places we saw on the same day.
I bought a house before and attended a number of open houses. I signed my name on a sheet but was not asked to present ID. In some cases (I guess where the realtor figured I wasn't going to buy? Not sure) they just let me walk around and paid no attention to me at all.
It isn't a public space so you can be barred from entry and, often, you'll be let into the house by a realtor. If that realtor recognizes you as abusing open houses they can just refuse you entry or take a more extreme measure.
Realtors are there to sell houses. I wouldn’t be surprised if most of them had a keen “nose” to figure out who is just “interested” and who means real business. After all it is in their best interest to not waste their time with lookie-loos.
Obviously that doesn’t mean that one can’t pretend well enough once or twice, but not at a scale where this becomes a viable avenue to criminals.
Having bought a house, I sure would be surprised. And IME if they don't think you look like you're gonna buy the house, they just let you walk around but ignore you.
From a house selling perspective it's probably in their best interest to simply ignore those people. Buyers with large pockets can come of as lackadaisical.
Your speculation is contradicted by thousands of open houses every weekend.
Seriously, go visit one and see what it's like. It's not the CIA Headquarters, it's usually a minimums wage newbie agent squatting in a house advertising for clients.
