Source: http://www.sodahead.com
As I wrote earlier on this blog, I’m reading Heffer’s Strictly English (2010). In chapter 4, called Bad Grammar, he discusses the difference between into and in to. I never knew there was such a distinction in English! Is there really? So lets ask our readers, I thought: which of the two would you use when something like the event in the picture happens to you? And if you feel like it, please explain why you preferred one or the other (or perhaps both, or even neither).
Bridging the Unbridgeable 
I would distinguish between the two: “I walked in to the shopping area” (the shopping area was inside something else and I was going through the something else to get to the shopping area). “I walked into the shopping area” (the shopping area was my destination and I walked inside of it). Subtle difference and, when spoken, intonation would indicate which was intended.
I think I would generally use into as a preposition and in to as a verbal particle and preposition, as in log in to the website.
Yes, I agree: you [log in] to a website (Dutch would require [op=on a website]). But do you [walk in] to a lamp post? That is what Heffer argues, basically because you can’t walk [into a lamp post].
But you can’t bump in to a lamp post. You bump into things.
That seems very odd to me. I don’t think I’ve ever heard a rule like that before. Does he think that you can only use into when you’re going inside something? If so, that seems to be an overly literal take on the rule.
yes it is, but that is his general (and annoying I must say) attitude he takes to usage problems.
I would only walk in to a lamp post if I walk into a place that has a lamp post in it and I then approach the lamp post. That may be too literal, but that’s also what Heffer seems to do. His argument isn’t based on syntax, his argument is that you shouldn’t use into since you can’t physically be inside a lamp post.