Done selling on eBay, they are demanding my social security number to sell

it asks if you are an individual or a business.  I looked at the business options. They had I think 3 categories that I did not fit in so they said I was an individual. Still want my SSN.

I get the big picture, eBay wants and will get the seller fee that PayPal has been collecting. Must be a tremendous amount of $$$.

It just flies all over me that they demand my SSN before they will allow me to sell.

I was told by the eBay rep   that they are eventually moving everyone to managed pay. Once you are migrated, PayPal will not be an option for you to accept payments on eBay. Not everyone at once, but the goal is to get it done over the course of this year. So sooner or later you will either agree to be migrated to this program or you will not be able to sell. 

I guess I will eventually give in. In preparation, I opened a checking account to be used only for PayPal and eBay so they won't have access to my primary account. 

 you have to pay back all sales taxes you’ve received. Correct?

no, you never receive it.. they collect it from the buyer and send it to the states.. it does not come to the seller

Why else would they want our SS#?

so they can report your income to the IRS. Until recently millions and millions of dollars of goods were sold through eBay and other sites without any sales tax being collected and without the profits being reported as income. The seller could easily run a business on eBay and evade paying any taxes. The buyer could avoid paying any sales tax.

That has changed now.

anybody that buys things and sells them for a profit has a potential tax liability. That's how business and tax systems work.  The seller has no tax liability unless they make a profit so you are incorrect.,  you don't "have to pay taxes when you sell it too" unless you are making a profit. 

In most states buyers are supposed to pay sales tax when they buy something. Doesn't matter if it is here or eBay or a local thrift shop or wherever.

There is nothing crooked about it. 

Nothing about the tax laws has changed in this regard. It has nothing to do with politics. What has changed is the tax collectors are catching up to all the people who were illegally evading taxes by dealing direct on the internet.

What this negates is people cheating on their taxes. If you approve of that as a "business model" then nothing I can do about that.