Domain sales/ transfers

One of the considerations while selling a domain at a marketplace like Sedo is the ease of transfer. At Sedo, the funds were released to your account soon after the transfer is completed.

On the other hand, GoDaddy has a confusing transfer process, where it is not clear how the funds will be released to your account after the transfer and there is a mention of a 20 day wait period. So a customer may initially agree to the transfer and then refuse to actually transfer the domain due to lack of clarity.

Web hosting risks

When you purchase hosting from any company, one of the big risks involved is that they may suspend / terminate your account without any reason. This is the reason, you should always purchase spare hosting capacity, to keep it as a standby. If one web hosting account is not working, you should be able to switch quickly to the other option.

"Office" for an online business

Unlike a brick and mortar business, which has a formal office / shop where customers meet the seller, or purchase a product or service, an online business can be run from anywhere in the world. Most websites are hosted at data centers which may be located in a different country or continent. The website can be accessed and modified from any part of the world where an internet connection is available.
The “office” for an internet business is just a formality, an address to receive postal correspondence.

Receiving emails

When you have a large number of websites,  you list your email address on the website for contact.  Then anyone can send you an email, you have no control over who sends emails to you and have no idea about their background.

Disadvantages of using ad networks

If you sell advertising on a large number of websites,  you will usually use an advertising network that automates the ad selling process.  However, on the internet, some of the ad networks do not have proper systems in place, so an unscrupulous ad network employee ( or some times owner ) can try to harm you or spread false rumours so that they can take over your websites for free or a low price. 

So it is better to sell at least some of your ad inventory manually, at least there is some clarity on the ownership of your websites. It takes time and you may get a lower price, but at least some of the rumours can be squashed.