There is so much spam on the internet that there comes a point when you learn to just ignore it. Realize that most of it is not targeted directly to you in terms of a personal threat but to a wider group in general. There are some sites that seem to be more prone to scams - craigslist being one of them.
The only time many of the scams are a problem is if you reply to them. If you just delete they usually stop because whatever program they are using to seek out emails requires a response as it verifies the email address for it to continue.
I like to use a web based email such as gmail for my daycare emails as it has a good spam filter rather than using something more personal such as the email that comes from my internet provider. That gives you one element of separation.
I do feel that the benefits of online advertising for sure outweigh the concerns but obviously take precautions. If it feels odd when you read the email don't answer if you don't want to. Never give out information such as address or phone on first contact - either can be used to trace you. Have all contact be by email - I like having it all in writing - until it sounds more sure. Most scams won't keep it up very long before they move on to someone else hoping to get the info they want on the first try.