The penny on the street had a disclaimer..it was not used to illustrate unauthorized wifi usage..it was used to illustrate proximity of the offence, per the disclaimer on the original posting. Readers are advised to read the whole posting, as the previous sentences provides the context for proximity.

If the penny was inside a house, undoubtedly it would be a serious offence..hence similar analogies of having a open door, open car door with keys etc..

However, the penny, or a wifi connection is usually encountered outside of the owner's (penny or wifi) property...so now the offence has a different context.

Couple proximity with low intensity (I used a penny to illustrate this, versus 1 GBP or 1 million dollars), the offence of checking emails of another person's wifi connection is of an extremely low magnitude.