Think of hotlinking as taking something that someone else has paid for and not repaying them for it. That would also be a definition of theft.
Most people who have web hosting services have a daily, weekly, or more commonly, monthly bandwidth allowance. What that means is if data transfer goes over that allowance, one of two things can happen:
First, the hosting service can simply shut the site off from the Internet until the bandwidth meter resets. This frequently happens to people who have their websites and the images on those sites hosted on free webhosting services such as geocities. But, it can also happen with people who pay for their hosting as well. Depending on the hosting service's Terms Of Use, this can be for a matter of hours, days, weeks, the rest of the month, or any time until the meter resets and starts counting data transfer over again.
The other thing that can happen for people who have paid hosting is that the hosting service sends notice to the owner of the website hosted on their servers to pay more money for the excess use of bandwidth.
Any time someone uses another site's URL to call-up the image on their own sites or boards instead of hosting it on their own website or image storage site, that is directly using the other site's bandwidth, or data transfer. Any time a visitor views a page with the directly linked image, data is called up from the hosting server, and they do keep count of the number of "hits". For many people, they can see how much data transfer is being used by various methods, such as a bandwidth meter in their control center at their hosting site, or more commonly for people who have paid hosting services, by browsing through their log files.
Bandwidth theft or hotlinking is also a serious problem for many webmasters and one of the reasons why they choose to close down their own sites or remove their images. It is also against Ezboard's Terms Of Use.
What can happen if people are caught hotlinking on Ezboard?
If the person is reported to ezboard legal and it is determined that the site is directly linking to someone's images, those images will be removed. If it continues, ezBoard can shut the site down.
The person who is hotlinking is also at the mercy of the person whose image they are directly linking to. What this means is:
1. The person who is having the image hosted removes the image completely and the direct-linking person is left with broken images, the dreaded red x's.
2. The person who is having the image hosted can replace the hotlinked image manually or automatically (usually through an .htaccess file) with something totally unexpected, such as a porn image. (I've seen it happen and it ain't pretty!) That's obviously humiliating and it also points out to every visitor to a site or community that the person was stealing.
3. The hosting service can shut the images off because of excess bandwidth useage. This would not only affect the person who is having his or her own site or images legitimately hosted, but it would affect innocent visitors to the site as well.
I hope this explains a bit more about bandwith theft/direct linking/hotlinking. If anyone is at a loss for where to have their images hosted, there are many places on the Internet that offer free hosting services for images, often enough to maintain personal avatars, icons, and sig pics. Most Internet Service Providers offer some space for free as well, but most people have to either ask for the service or do a little investigating to find out where to sign up for this.
In the end, there is never any reason to steal someone's bandwidth.