How would you implement an automatic way of the images loading in a pop-up (lightbox/colorbox) window by a click? What I mean is, can we achieve the blogspot.com/Blogger experience where we can add photos to the content (node in Drupal speak) and without any ado (adding class="colorbox", or enclosing the &lt;img&gt; element into an &lt;a&gt; ), clicking the photo in the post will make it enlarged in a pop-up window, similar to how colorbox functions.  

I have visited this question Configuring Lightbox2 to Pop-Up Images embedded in nodes and it seems ambiguous to me.

I have a current Drupal 7 site and it's quite annoying that I have to manually enclose the images in a

&lt;a class="colorbox colorbox-insert-image" href="..." title=..."&gt; ... &lt;/a&gt;


every effing time.
You can. As always, there are several ways.

You can implement a Drupal behavior (jQuery script) that finds all images within the content and adds according classes / click callbacks.

Another way would be writing a little custom module implementing a content filter that does the same on your server.

I'm not at a PC right now. But I think you have two viable ideas now to search for. Let me know, if you need further help.