Internet con-artists - Beware!

Hi all, I've noticed recently there seems to be an alarming number of con-artists online. They target online job applicants and people selling property online.
We put our property up for sale on a website and got some "strange" emails, not the usual inquiries. A gentleman who goes by the name Aldo mailed us. He gave a UK telephone number. He didn't ask important questions regarding the property, instead said things like he's got the funding sorted to buy our place and he's "willing to buy" our property etc. What got us suspicious was his questioning and the things he said. He talked about buying our place sight unseen, not really knowing much and didn't seem interested in finding out more. After a number of mails he asked that we put together a property proposal for his bank. Why should we do it for his bank if he's the buyer? He also asked for papers proving that DH is the owner of our property and he wanted proof of his identity etc, which we refused to give. DH asked him some questions and he disappeared like smoke.
A friend of ours sold their house recently. They told us they had a prospective buyer phone and say "I love your place, I want to buy it. Give me your bank details and I'll pay a deposit." Needless to say they didn't!
Another friend told me about their battle to get her DH a job. They apply online, have to pay fees to the recruitment agency and never hear from them again. They recently had a job offer via email from a company. 7 Pages of questions included. I said to her I find it funny that the company will offer her DH such a senior position without interviewing him first... She phoned the company and they knew nothing of the email or the job offer. Someone used their name to get my friend's DH's personal details.
So please be very careful when you deal with people online. Don't be shy to ask questions, if the people you deal with are honest, they will not mind.
If any of you had a similar experience please let us know, so we'll know what to look out for.