Personally I don't like spaces because every now and then I find a service that doesn't accept them - ex: you can't have spaces in your IRC password. ASCII printable characters are enough for me.

Look at the difference in time when using a simple 'helloworld' password with and without spaces. https://www.grc.com/haystack.htm

Also, for some more reading on why using spaces will make it infinitely more difficult for hackers to try and gain access: http://www.baekdal.com/insights/password-security-usability

There's one ilovemydaughternancy with no spaces. Why would you want spaces?

There's also lovenancy18. Someone will have a long talk with his daughter.

Sentences are easier to remember. Yet grammatically correct sentences can give you things like capital letter, whitespaces and even periods.

Unfortunately, they also cut down on the search space quite a bit.

I find that typing a bunch of words with spaces is faster than with words. I guess my brain is wired by now to automatically press the spacebar between words.

Wouldn't it make it harder to remember which places accept a password with spaces and which don't? I already have trouble remembering which sites require long passwords and which require shorter ones.

to make it more natural to type a passphrase