I am not sure how effective those copyright widgets are against content theft. But sites like myFreeCopyright they may act as as evidence in proving the ownership of the content if it is copied by someone else.
There exists nothing like copyright-ing your works which few think is true ( Not sure what the verb form of copyright is :-? ) Every article that you write is your own and no one is entitled to copy them unless you explicitly give them the permission to do so.
Sites like myFreeCopyright.com (mfc) help you in proving that you own some article which has been copied by someone else. Whenever you publish an article, you need to go to the site and enter the URL of your blog post. A copy of that page will be stored on their server. Later, if someone claims an article written by you as their own (after publishing the same on their blog ), you can use the page stored at mfc as an evidence.
But I am not sure if this really works. Consider the situation where A posts an original article on his blog. B copied A's article and registers the URL at mfc. Now, is B entitled to claim that his article had been copied by A because he had registered the URL at mfc?
Generally when claims are filed to google, they decide which article is the original one by looking at the credibility of the sites. ( This is what I think is true ) For example, if a person A copied an article from The Hindu website and files a DMCA case, it is highly improbable that 'The Hindu' would be penalised for it. ( even if he shows an evidence from mfc )
But still, if you find that someone has copied your article, you are always encouraged to file a complaint.
As TS mentioned, the widgets at times may also encourage someone to copy your article! Moreover, those widgets consume some space on your blog which could have been used in a better way. On the other hand, some people put up some banners saying that their articles are under 'Creative Common License' or something similar. These kind of banners are required because it is not assumed that content is not allowed to be copied unless explicitly told.
Disabling right click is not a very good option. Those who want to copy your content will anyway copy it by disabling JavaScript. Moreover, it can be problematic if someone wants to copy a word or a phrase from your blog for some other purpose. For example, if someone mentions about X which has aroused my interest in it, I simply select the text > Right Click > and select 'Search Google'. Some people disable selection and right click and it really annoys me. ( I feel a bit lazy to manually type that in Google :( )
And now for all those who are reading this article, I wish to say something. Many bloggers post images on their blogs without mentioning the source or stating it to be 'Google Images' ( which is actually not the source ) Just as we do not want our articles to be copied, those who own their images may also frown at copying their images. So, it is always recommended to state the source of the image with a link to that page. This will also probably help in conveying to Google Image Search that the original owner of the image is that other site and not yours.
( Just joking! 
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