For some small applications, it can be handy to eval a configuration file that is simply a language data structure. It's like having a built-in config file parser. It also gives to lots of flexibility with your hacks :)
Some languages are nice enough to provide functions that parse the text into native data without the need for evaluation (like erlang's erl_parse/erl_scan; I guess lisps can do the same)
That's why I said "Just because you can, doesn't mean you should" and not "Don't even think about it". 'eval' exists for a reason, and there are certainly good reasons to use it. This is not one of them.