There was a time when we used to joke that usenet had the same 100 posters, all posting to different subsets of groups. Basically, it took a bit of technical nous to get on to usenet in the first place. We had newsgroup meets and met people in real life, and, with very few exceptions, most people proved to be OK.

Nowadays, 98% of he population is on-line, search engines have improved out of all recognition, and it it is really easy to look up someone's name and find out their complete history. I certainly don't tell my different groups of friends everything about myself - I'm not going to start making my whole life visible to complete strangers on the internet.

Remember too that employers nowadays will do internet researches on potential employees. There are things you do in your leisure time that you might not be happy about revealing to your employer.

I doubt whether the proportion of undesirables in any higher, but with a much greater number of people posting, the absolute number of undesirables is greater than it was. And every extra undesirable who manages to pick up real-life information about you just makes life that little bit more complicated. And there are certainly urglers who have met people on urg who have turned up in real life and made things difficult.