I think it's made us more efficient.
Sure, I could memorize a ton of information for work...or I could just google it. I do on-site desktop IT support at my work; I work so much faster because I can just "google" things instantly to learn how to do them or solve a problem, rather than spending hours or days trying to solve a problem, or have to resort to nuking a machine just to get the user working ASAP again. The trolls would argue that real IT people should learn how to fix the problems, but I support over 200 users in a 3-shift environment, so time is money, and uptime is king. Thus, the Internet is awesomesauce :awe:
I think the anonymity brings out the worst in some people - Youtube comments being the prime example. Youtube is really useful for entertaining videos or learning how to do something like cook a meal or fix your plumbing, and the comments could be really useful as well, but most of them are trash. I also don't think that Youtube etc. has contributed to a reduction in attention span - I think it's just catering to how humans naturally work. Commercials on TV & radio used to be long, but then they got short - and that's about all the attention span we have lol.