Just because yu've never heard of them doesn't mean they don't exist. Have you ever heard the saying "just because the masses agree that doesn't make it correct"?

Here's a wonderful letter that eBay sends sellers advising them of their selling limits:
"Hello XXXX,

This message is to notify you that in order to assist you in building a
strong foundation for future transactions on eBay, we have placed a
selling limit for your listing activity. These limits are not in place
as a consequence, rather as a preventative measure to help our seller's
keep from becoming overwhelmed with large increases in account activity.


Many members already have limits placed on their account. Account limits
allow us to learn about your selling activity and make sure you're
adhering to our selling practices policy and performance standards.
Limits vary by seller and can change over time.

During this time, we want to confirm you are continuing your positive
history by ensuring you are keeping focused on creating great
transactions for your customers. Doing so will greatly increase the
chances of an ongoing successful eBay business and help to avoid any
future account issues that may arise. These limits will allow you to
continue selling while also allowing us to monitor your incoming
Feedback, Detailed Seller Ratings, and any customer complaints. Please
understand that the actions we have taken do not mean your account
performance is not good, but we do this to help all eBay sellers further
improve their selling history and account performance.

Because you are doing well at selling at these volumes, you should not
hit your selling limit unless you dramatically increase your sales.
However, if you do wish to grow your business, we will gradually
increase your limit as you show that you are able to successfully handle
the higher sales volume. The selling limit on your account is based on
the number and dollar amount of open (active) items and successfully
sold items per calendar month.

You can now sell up to X items monthly or up to $Y monthly.
(Keep in mind that this includes multiple quantity listings which can
greatly influence this number.)

If you do reach one of these amounts during the course of a month you
will be unable to list additional items or increase the price or
quantity of your active items until some of your items end without a
winning bidder or until the 1st of the next calendar month, (If you are
still exceeding the selling limit at the first of the next calendar
month your selling activity will continue to be blocked.)

We believe that your limit is flexible enough to allow you to sell any
current items and is in accordance with the volume you may have listed
in the past. If you do reach the selling limit on your account and want
to increase your sales, please work within the amount for at least 30
days. Once that time frame has expired on XX/XX/2011, please reply to
this message and we will conduct a review to see if adjustments are
appropriate.

We hope that you will use this selling limit to your advantage and focus
on succeeding with your current sales. We value you as a seller and hope
to work with you in order to continue to establish a strong selling
history and successful business relationship. It is in our best interest
to help our sellers succeed so that we can have a positive trading
environment and eliminate bad buying experiences on the site.

If you need further assistance, please don't hesitate to reply to this
email and let us know.

Sincerely,

Chris
eBay
Customer Support"