Erm... maybe?

If I've understood:

1. This is an issue, but by reading the forums you can usually figure out who might be a scammer or not.

2. You can check the code yourself to see what the miner software does - it doesn't do much that's exploitable. Because of the way the pools work (as I understand it...), it's to the pool's advantage to feed the miner valid data.

3. I think this relates to point 1, in that you have to pick carefully and then assume they're as trustworthy as you hope when you estimate your likely profit. As with any time you're trying to turn a profit, your costs (electricity, hardware, repairs, etc.) just have to be included in your calculations.

--Tom