Why is font always defaulting to Lucida Sans in authoring?

It sounds like your browser's default font is set to Lucida Sans. PBwiki doesn't set a font face by default. Take a look at this page. The first 5 lines are the default font, and the second 5 lines have been manually changed to "Arial". Here's part of the source:

<p>Default Font</p>
<p><span style="font-family: Arial;">Arial Font</span></p>

As you can see, the "Default Font" line has no font specified; the "Arial Font" lines have Arial specified.

There is no way to have PBwiki automatically apply a specific font-family to page elements; it must be done manually.

Without going into details, your remark as there is no way to have PBwiki automatically apply a specific font-family is, what we call over here, BS.
Six occurences of 'font-family' in PBwiki's 2.0 stylesheet when we stopped counting, the most important ones specifying Segoe UI (where the h*ll is that?), Lucinda Grande and Arial, in that order.
Our dear friend, MacUser, explained here how it works.

Well, "Chuck", you should try some details next time, because you are wrong. The "font" button in the PBwiki Editor uses a span to apply the font; there is no way to have that span automatically generated and applied to page elements (the crucial part of my quote that you left out for your convenience). CSS is also a dead-end, as there is no way to have PBwiki automatically assign class or ID tags to page elements, either. Even if you buy their "CSS Support", you would still be limited to re-styling existing classes and IDs, because you can't tell the editor to automatically apply your own classes and IDs to page elements. Sure, you can use the built-in classes, and some of your page elements are covered under some of those classes. But there is no way for a user to have PBwiki automatically apply that CSS to a page element (unless it's already applied by default). The user has no control over that.

I hope all those blows to the head haven't addled you too much to understand what I'm saying here, Chuckles. Feel free to provide a link to a working example, if you feel that you can "have PBwiki automatically apply a specific font-family to page elements", without doing anything manually.

Jeez, so sorry to upset you, Guy.
I might have interpreted the original question differently (why is font defaulting to Lucida?) and I don't know for sure if I understand your answer, isn't it waaay out of context? I reacted to some of your statements which in my belief aren't true, to me 'automatically' and 'specific' are contradictory by nature, you do have a conveniently way of quoting urselves and making it hard for me to understand your logic. Let's be friends, OK?

This discussion is really about the WYSIWYG editor and its peculiar behavior, in this case not expanding the chosen formatting to inserted links or table rows.
And I have to disappoint you here, I don't know how to solve this, I barely use the editor, dive directly into source mode, whatever our dear friend, the Vu Man, may think of that.
Lately, on another platform, I have been using other editors which have a built-in way of applying pre-defined div & span to page-elements. PBwiki 3.0?

However, maybe the person asking the original question is better off applying some general CSS styling in his/her Sidebar, telling the wiki to display everything in Arial? Or do it page level, by putting everything into a div with styling (in source mode and then don't touch those formatting buttons no more ..)?