hydroplaning? what about dog poo planing

Tim at twisty.com has been talking about why people prefer to buy bicycle tyres with tread on them. He pointed out that people like to use tread as a gauge so that they can see when they need replacing, The post he references argues that you would need to be doing 90 – 100mph on a pushbike to hydroplane. I can confirm that as a rider of a mountain bike with slicks (well one slick, but thats another story) that you only need to be doing 2 – 3 mph to "plane" on random goo such as soggy paper, cardboard, vegetables and dog’s eggs you encounter on the UK’s roads and pavements, so I prefer tyres with tread because I believe (rightly or wrongly) that this will help me "cut through the shit" so to speak.