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" did "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.
Plenty of linguists would admit 'login' as a verb. There is very little difficulty in accepting that 'to log in' and 'to login' mean the same thing.
In this case "in" does not function as a preposition, it is part of the verb. The evidence for this is immediately apparent when we consider that "to log" and "to log in" really are two different activities. We do not mean that we record anything when we login to a machine, what we are doing is obtaining access to it by means of an exchange of previously established authenticating information - and while this step may involve making a record of our login, it need not for the basic sense of that action to remain intact.
Also, we have no trouble with a multi-word verbs in English, if you don't believe me, try googling 'phrasal verbs'. This article is either a gag, or really is just an example prescriptavist nonsense which attempts in futility to combat the last 50 years of linguistic consensus.