Hiding Directory Path

The easiest way to achieve this is to add,

Options -Indexes

..to your .htaccess file.

Specifically your .htaccess file should look like this,

# BEGIN WordPress
Options -Indexes 
...etc
...etc
# END WordPress

This is one way and probably the most efficient way.

This method will prevent any direct access outside of blog posts, pages, or template files which call any images or files from this directory.

A usual read overall:
http://httpd.apache.org/docs/current/mod/core.html

Access to the /uploads/ folder should not pose a security risk, in theory, (retracted aforementioned statement – if your permissions are set incorrectly you may expose yourself to harm)