You never know what agents might do. However, in our area, if you follow MLS requirements, the listed property must be put on MLS. 

There will never be a shortage of unethical real estate agents.

Some agents do this, but all listings must be put into the mls within 4 days of signing the listing agreement.

Dont have any pocket listings.

If the seller does not agree for the listing to be on MLS, it does not go on MLS.

Mike - I sold a home before I ever even put up the For Sale sign, so it never made it to the MLS.

This is really up to the broker and MLS policy.  In MA, once the listing agreement is signed, the agent must post the listing immediately on the MLS or file with the Service a delayed listing agreement signed by the seller indicating when the home will be added to the MLS, but then no marketing can be made until such time.  If it is truly a pocket listing, or an exclusive right to sell with consent to dual agency and a waiver of MLS cooperation, then this needs to be ok with the broker and on file with the MLS.

we can enter with pend at listing.  and yes I put it in when it closes and immediately change it to sold.  It becomes a comp for agents to use that way.

My company requires it to be put in MLS to count as a transaciton. So I would enter it then immediately pend it.

In the CA listing agreement the seller can opt out of the MLS. If they did not, you must list and change the status to pending or sold, adding something like ''sold before processing''.

Once we have a legal listing we have 3 days to put it on MLS.   We are also required to put it on the MLS even if it sells right away. 

Not all listings put on the MLS and pended right away are pocket listings.  I have had some that are expired and I brought them a buyer.

It just depends on the clients.  Most of the time I do not put it in the mls at all, mainly just to protect the clients so no one can see the previously sold data. 

I do not do pocket listings. I have seen several agents to it and do not think it is in the Seller's best interests. 

Mike,

Does not appear on the MLS.  

My actions are determined by what the seller has authorized me to do. If it's a pocket listing with no commission to buyer's agent, then I do not put it on the MLS.

There is a reason they're called pocket listings and attaching MLS to that reason defeats the Seller's purpose. Don't expect to earn any future profit from this tactic in your niche. 

Here we see an occasional listing added after settlement "for comp purposes only", often with no photos or other particularly useful information.

Of course.

It is MIRACULOUS I can secure a buyer for house one day after I publish it on  on the MLS.....and have back ups!

I haven't had a true pocket listing but I know of examples of the situations you describe.