Aren't password crackers aware of that by now. I wouldn't use common sayings, movie quotes, literary quotes, song lyrics, etc., but something more personal.
True, I was just using a common one as an example. You should definitely choose something more specific to you.
The point of having upper and lower case, numbers and symbols is that the pool of possibilities for each character is enlarged massively. Instead of 26 letters, you have 52, plus 0-9, and whatever symbols are allowed. It makes a dictionary attack useless, and a brute force attack much more difficult.
So even if you license plate it, l33t it or just turn it to txtspk, unless it's the current hot catchphrase or song title, it's unlikely to be broken, and yet is easy to remember.
A couple points. One, just making those characters available expands the character space; requiring them for everyone doesn't add anything to that. IN fact, if I know passwords require special characters and numbers, I can immediately through out a standard dictionary attack, because I know your password can't be a dictionary word.
In addition, most dictionary attacks these days include common substitutions, like 3 for E and @ for a and so forth. Relying on "license plating" or txtspk is not safe.
Also, can't recall who mentioned the hashed passwords as being a server problem, not necessarily. Hashed passwords are also what gets sent across a network. Now hopefully, the connection itself is encrypted, but not always. Not to mention passwords (well, hashed versions anyway) are often cached locally on user machines, at least for some small number of users (often the last user, sometimes the last three). To add to that, if I can compromise a single user's system (say, your sales guy with that laptop he connects to public networks while he's travelling), then I can put software in it that will sniff out hashed passwords on the wire when he gets back to the office network.
Just FYI, this particular type of crack (attacking a list of hashed passwords by trying to match hashes) is called a Rainbow attack, IIRC. And it's not just brute-force, often they'll use a dictionary, along with l33t speak and text speak substitutions, as well as lists of common passwords. And it's MUCH faster because everything is local.
But generally, there does have to be a security failure somewhere for an attacker to gain access to hashed passwords, just doesn't have to be the server.