diff --git a/core/lib/src/data/from_data.rs b/core/lib/src/data/from_data.rs
index c5cdb75f..46108175 100644
--- a/core/lib/src/data/from_data.rs
+++ b/core/lib/src/data/from_data.rs
@@ -1,4 +1,3 @@
-use std::io::{self, Read};
 use std::borrow::Borrow;
 
 use outcome::{self, IntoOutcome};
@@ -289,6 +288,9 @@ pub type Transformed<'a, T> =
 ///
 ///   * **String**
 ///
+///     **Note:** _An implementation of `FromData` for `String` is only available
+///     when compiling in debug mode!_
+///
 ///     Reads the entire request body into a `String`. If reading fails, returns
 ///     a `Failure` with the corresponding `io::Error`.
 ///
@@ -299,6 +301,9 @@ pub type Transformed<'a, T> =
 ///
 ///   * **Vec&lt;u8>**
 ///
+///     **Note:** _An implementation of `FromData` for `Vec<u8>` is only
+///     available when compiling in debug mode!_
+///
 ///     Reads the entire request body into a `Vec<u8>`. If reading fails,
 ///     returns a `Failure` with the corresponding `io::Error`.
 ///
@@ -307,7 +312,7 @@ pub type Transformed<'a, T> =
 ///     memory; since the user controls the size of the body, this is an obvious
 ///     vector for a denial of service attack.
 ///
-/// # Simple `FromData`
+/// # Simplified `FromData`
 ///
 /// For an example of a type that wouldn't require transformation, see the
 /// [`FromDataSimple`] documentation.
@@ -398,15 +403,15 @@ impl<'f> FromData<'f> for Data {
 /// A simple, less complex variant of [`FromData`].
 ///
 /// When transformation of incoming data isn't required, data guards should
-/// implement this trait instead of [`FromData`]. For a description of data
-/// guards, see the [`FromData`] documentation.
+/// implement this trait instead of [`FromData`]. Any type that implements
+/// `FromDataSimple` automatically implements `FromData`. For a description of
+/// data guards, see the [`FromData`] documentation.
 ///
 /// # Example
 ///
 /// Say that you have a custom type, `Person`:
 ///
 /// ```rust
-/// # #[allow(dead_code)]
 /// struct Person {
 ///     name: String,
 ///     age: u16
@@ -556,6 +561,9 @@ impl<'a, T: FromData<'a> + 'a> FromData<'a> for Option<T> {
     }
 }
 
+#[cfg(debug_assertions)]
+use std::io::{self, Read};
+
 #[cfg(debug_assertions)]
 impl FromDataSimple for String {
     type Error = io::Error;
diff --git a/examples/content_types/src/main.rs b/examples/content_types/src/main.rs
index 83c6bcdf..419e4d7a 100644
--- a/examples/content_types/src/main.rs
+++ b/examples/content_types/src/main.rs
@@ -2,12 +2,14 @@
 #![plugin(rocket_codegen)]
 
 #[macro_use] extern crate rocket;
-extern crate serde_json;
 #[macro_use] extern crate serde_derive;
+extern crate serde_json;
 
 #[cfg(test)] mod tests;
 
-use rocket::{Request, response::content};
+use std::io::{self, Read};
+
+use rocket::{Request, response::content, data::Data};
 
 #[derive(Debug, Serialize, Deserialize)]
 struct Person {
@@ -28,10 +30,16 @@ fn get_hello(name: String, age: u8) -> content::Json<String> {
 
 // In a `POST` request and all other payload supporting request types, the
 // content type is matched against the `format` in the route attribute.
-#[post("/<age>", format = "plain", data = "<name>")]
-fn post_hello(age: u8, name: String) -> content::Json<String> {
+//
+// Note that `content::Json` simply sets the content-type to `application/json`.
+// In a real application, we wouldn't use `serde_json` directly; instead, we'd
+// use `contrib::Json` to automatically serialize a type into JSON.
+#[post("/<age>", format = "plain", data = "<name_data>")]
+fn post_hello(age: u8, name_data: Data) -> io::Result<content::Json<String>> {
+    let mut name = String::with_capacity(32);
+    name_data.open().take(32).read_to_string(&mut name)?;
     let person = Person { name: name, age: age, };
-    content::Json(serde_json::to_string(&person).unwrap())
+    Ok(content::Json(serde_json::to_string(&person).unwrap()))
 }
 
 #[catch(404)]