I agree that running tail on error logs is a useful development technique, but I would never do this on a live server.

tail doesn't check its output, so a malicious visitor to your Web site could send dangerous escape codes to your terminal. xterm, for example, has various features/vulnerabilities that are based on escape codes. This assumes that someone wants to attack your Web server and either knows or guesses that you are running tail on your error log, but it's always worth protecting against untrusted data on the Internet.