Ways not to lock your bike

I always take my bike in with me when im lock-less, its no bigger than a shopping trolley or a pushchair. Get some funny looks but noone has complained so far...

Was on my way out of Tesco's the other day and saw a bloke with dusty lycra and top-range Sidis shopping, obviously after a long ride. Got outside and as expected his expensive Trek was leaning against the wall well away from the doors unlocked. Three lads walked by and one went to take it but the other two stopped him when they spotted me, I even hung around till he returned to his bike.