FrontPage Users
Enabling ANON FTP on a FrontPage created site can expose private site access information within the user's /_vti_pvt directory. The permissions on the FrontPage directories are, by default, 755. As with any other anonymous FTP usage (this is only an issue on AFTP-enabled accounts), you need to ensure that the public permissions are tight enough to prevent access to those directories. chmod-ing the _vti directories to 700 seems to do the trick - it prevents those directories from being browsed through anonymous FTP.

Security
Anonymous FTP will grant any and all users the ability to access your "upload" directory, or any directory on your domain that has been set for "public" read/write permissions. Anonymous users will have access to upload or download files to and from your domain. You must set the appropriate permissions for your directories to restrict anonymous FTP access. This is needed to ensure that anonymous users will not be able to access any existing files or directories. Anonymous FTP access is only available in the "anonymous/" directory.

Responsibility
As the account owner, you are responsible for any and all files that are stored on your domain. This would include files that were uploaded by you as well as by anonymous FTP users. With the use of anonymous FTP, your site is susceptible of becoming a "warez" site. Typically, these are sites that are used by "hackers" to trade (upload/download) illegally pirated copies of software programs with one another. As the account owner, the complete content of your account is your responsibility. If your site becomes a trading post for "warez" programs, you may face legal action that can be taken against you by the programmers/software companies of the copyrighted software.

Data Transfer
Any and all FTP download transfers, anonymous FTP included, will be used in the calculation of the total data transfer for your account. If this total data transfer amount exceeds the limit that is set for your plan, you will be responsibility for any and all overage charges that occur. Please Note: There will be NO exceptions made for these overage charges. Once anonymous FTP has been enabled, it will be your responsibility to monitor the anonymous FTP activity for your account. All anonymous FTP activity is stored within the "xferlog" file. This file contains entries for each and every anonymous FTP upload/download session. This file is located within the /stats directory of your account. There is also a link provided off the "View your web usage statistics & logs" page of your account control panel. You can also have our servers perform certain actions when your data transfer exceeds a pre-defined limit that you can specify. In your "Edit Account Information screen look for the following section:

Disk Space
If you are going to allow people to upload files to your site, make sure you keep track of your disk space usage via your Control Panel. Do not allow your disk space usage to get too close to your maximum disk space allocation or you may experience problems accessing your site via FrontPage and/or be unable to upload or modify files. You may purchase additional disk space if necessary in 5MB blocks.