There's a spot in the ocean - can't remember where off the top - where the currents meet that's about 8 square miles filled with plastic bags and containers. Some floats, some is suspended in the water for miles down. Icky.
In terms of recycling, plastic is much more expensive to recycle than metals or glass. I try to buy things in metal/glass containers rather than plastic when I have the option.
The trouble with throwing things away into landfills is even biodegradable items don't degrade in that kind of high pressure, no oxygen environment. Things like fully intact apple cores and banana peels have been found in 100-year-old landfills. [Insert plug for composting here....]
A great way to remember to bring cloth bags is to leave them in your car so they're always there when you go shopping. While you're "training" yourself to always bring them in, you can refuse to use store bags, load all your stuff back into the cart individually after checkout, then load individually into your car. A good reminder not to forget!
The one dilema I still have is the produce bags so I even reuse these because they don't get that dirty. You kindof have to use them for some things, although I have stopped using them for things like a single cucumber or peppers. Apples, though, you need something to put them in. And I have food allergies and don't want to put my veggies directly into the cart and the checkout belt in case they get contaminated.