Obligatory Link :-)
Let's turn this into a link in which the meaning of the prefix Ob is explained. Ob is a short form for obligatory and originated in USENET discussions and Internet mailing list discussions in which an individual was intentionally posting a message that strayed from the topic of the newsgroup or mailing list. In order to mitigate the fact that they had posted an off-topic message, the person would include a postscript to their message that began with a compound word beginning with the prefix Ob.
Thus on a mailing list about Wikis the postscript might look like the following:
Wikis don't lend themselves well to arguments which is why mailing lists still have a useful place for some people.
Some people take the form to extremes by writing an entire sentence in Wiki keyword style prefixed by Ob, for instance, ObWhyIAbsolutelyHateCodingInC++. I have also seen this combined with the perceived need to include an EmailDisclaimer? at the end of a message. Normally such disclaimers are in the signature block but sometimes people place them in a postscript labelled ObDisclaimer?.
At its best, the requirement to justify a link from some random subject back to the official topic can force novel insights. Rather like in poetry, where the need to form a rhyme can rule out conventional cliches and force you to be original. -- DaveHarris