For what it's worth, I've kept a running file based entirely off of what I've seen on this 123 page thread about what cards are likely to work and which ones won't. I'll post it here for anyone's edification, but I will not vouch for it nor can I say it's up to date, though nothing I've seen lately obviously overturns it all. If anyone knows better, just say so and I'll update my file:
Good:
Discover
TD Bank
Barclays
PNC
Associated Bank
Amex
Wells Fargo (not currently accepted)
Do all of the Good allow for adding and removing online?
No. Well at least not per Good Company. Their documentation says PNC is phone only. I have a PNC card just recently enrolled, but no AU sales yet so can't confirm that yet.
USBank owns Elan, but the two act independently as far as I can tell.
As far as the list goes, I think the picture is far more nuanced. Barclays doesn't seem to care a whit about AU activity, but they have a lifetime limit which I find pesky, although now I know how to deal with it. Chase is famous for closing down all cards, but I have my highest limit, oldest, best commission card with them that sells well and a second card that also does well and I've not yet been shut down (knock wood). USBank is not particularly known for shutdowns but they shut down both of my cards with them for AU activity...but then shortly after gave me two more cards. BofA is known for shutting folks down more frequently, but they haven't hit me yet, and philosophically I don't care because I have plenty of cards and don't have a very good opinion of BofA as a business (among other things they don't reallocate credit lines among personal cards without a hard credit pull, which I find a ridiculous policy). Discover sometimes asks for AU documentation apparently, which I imagine to be a hassle. Some issuers are easier to add/remove, but may not give as generous of credit lines and thus may have lower commissions. With some issuers the Good Company requires longer cycles (keeping the AU on for 4 months instead of three, for example). With some issuers the Good Company allows more slots. Some issuers might have some cards with good signup bonuses that can then be piggybacked later. Some issuers seem to have more difficulty posting to the AU's credit reports.
Overall my experience is that all the issuers have pros and cons. Some on average are better than others but all the ones I've had (which is most of them that Good Company accepts) are at least reasonable enough to work with based on the amount of effort involved compared to the payments. I have a long, littered credit card history from playing CC games for decades, and I have a lot of piggybacking cards going currently. My current practice is to look at which issuers I don't have a full slate of piggybacking cards with yet, then see which of those I think I can get more CL with, then look at DoC to see which cards at those issuers have a decent sign up bonus. But that's just my approach, YMMV based on your situation.
I've seen a couple people here mentioning companies asking for documentation of authorized users. This is, in fact, illegal for them to do, in accordance with the following:
12 CFR Part 1002 - Equal Credit Opportunity Act (Regulation B)
7(a) Individual accounts.
2. Open-end credit - choice of authorized user: A creditor that permits an account holder to designate an authorized user may not restrict this designation on a prohibited basis. For example, if the creditor allows the designation of spouses as authorized users, the creditor may not refuse to accept a non-spouse as an authorized user.
That is the law itself as updated August 29 of this year. Nothing new. When they ask for documentation, ask for their full name, then request to speak with a manager. Tell the manager that your brother-in-law is a top litigation lawyer and you'd hate to see a lawsuit over something so petty such as adding your friend to your credit card, especially when "John Doe" (the employee who you spoke with already) and "Jane Doe" (the manager you're NOW speaking with) are currently breaking federal law and not only have no right to request such documents, but have done so and could easily lose their careers over this. They'll add your AU right away and apologize, trust me.
Note: ONLY DO THIS IF 7(a) part 2 applies to you! Simple.
Edit because I'd like to mention that what I said above would be my personal approach to dealing with that situation. With that said, by asking for documentation they're breaking the rules of a federal act - whether they know it or not. By calling them out on that, your result may vary so don't take my example as legal advice or any kind of guarantee. Just wanted to make the facts clear.