I think it would be a nice core feature to have these implemented.
Currently, there are add-ons for this. However, while tabs doesn't seem to have any problems, the add-on for tables doesn't mesh too well with the rich text editor -- also known as WYSIWYG. Read through this, where you can also see what tabs and tables look like in my signature (current username is Volk).
Because the add-on doesn't mesh well in the rich text editor, the table code gets all scrambled up and you have to either disable the rich text editor in your preferences or work on the table in a document and then copy and paste it into the editor. Additionally, even when using the rich text editor, the bulletin board code still shows and not the tables themselves.
For tabs, this is how the codes works on the add-on:
[TABS] [TAB=Tab 1]Some content here.[/TAB] [TAB=Tab 2]Some more content here.[/TAB] [/TABS]