The number 1 negative effect is that people are not doing their own work anymore. Today more and more students are relying on the web to do the work for them. This can range from copying and pasting (plagiarism) to paying a web site to write a paper for them.
Studies have also shown net-based readers (people who do the majority of their reading on-line) are less able to determine what is and is not a valid source and are less skilled in critical reading and thinking.
Some science and technology are harmful to the earth--example pollution by artificial toxic chemicals, atomic bombs, "development" that threatens extinction for many species, sonar that kills dolphins--the list goes on. Responsible scientists and technologists can work to remedy the negative effects!