I'm beginning to think that linguistic prescriptivism is going to have a hard time holding up against the crazy mixing bowl that is the Internet and, to a wider extent, globalization. It's fun to play grammar nazi and all, but I've started to resign to the fact that people are simply going to do what they're going to do. Look at the state of English only a couple centuries ago. Language evolves quickly. Who's to say…
"Google" and "email" don't contain prepositions.
I log in. You log in. We all logged in.
I login. You login. We all logined. What? We all loggedined? We all loggedin?
If we just acknowledge that "login" is a noun referring to your credentials, where as "log in" (or "log on") means to supply one's login/credentials, then it's all hunky-dory.