I can't get worked up about 'can' vs 'may', as long as the phrasing and manner of asking are polite.
wanderings 
Aderyn, I guess I think it's OK, as a contraction of a grammatically valid structure (yup, descriptivist and proud of it). Do you think 'needs doing' is OK? A case could be made (not that I would agree with it) for that being more ungrammatical than 'needs done'.
The 'shop the dress' thing reminds me - I do dislike the 'edit' nonsense on clothing shop websites, and the habit of talking about 'a trouser' or (worse) 'a jean'.
'Buy' without an object. As in house buying - 'we're looking to buy in London' - or wrt Christmas - 'I buy for my family, dh buys for his'. It's not ungrammatical and the context makes it comprehensible, but it irrationally annoys me.
On the subject of housing: 'rented accommodation', or 'living in rented'. Urgh. The very use of 'accommodation' implies something temporary and precarious and therefore stigmatising. I assume that sort of usage is going to have to change as the number of people renting grows.