The only context in which I can see both terms arising near eachother would be in storytelling.
If an actor, with only a page of a script, must perform an act that fits into the story. The director must provide him with motivation for the action, must supply a motive, a reason for the act.

Without such direction the actor might be at a loss or forced to rely on personal experience to place the action into a context that allows its performance.
If the internal motivation for the action is wrong, the director might ask "Why did you do this this way? What was your motive?" and then supply a more appropriate context within the production, the motivation needed to provide the act validity in the continuum of the envisioned piece.
I do not believe either word really has a connotation that is positive or negative in general use, each refers to an aspect of an action. This suggests they are neutral descriptives.

I see the problem of one in which terms used from a science are finding their way into common usage. Often such events are followed by periods of abuse and misuse.

Events, like a sudden epidemic that changes the way a society or large populations address mundane issues like changing outer garments before entering the rest of a home, are societal events. If someone needs to feed the survivors, this is a social issue.

There are, just to be contrary-- also situations where no space after or before is appropriate if not absolutely correct. In byline- dateline it is often the case that the byline receives no space but the em-dash takes one before the dateline.
In situations, rare though they be, where the author is stressing the moment of an event, the parenthetical phrase is preceded by a space, even when it follows an em instead of parens or commas at its beginning. If the initial thought is completed within the sentence then the parenthetical closes with a comma and the rest of the sentence progresses as if nothing had happened. The most frequent and annoying occurrance of the described usage-- is in fiction and, must be well constructed to avoid the hungry red pencil of an editor who reads it differently.

The usage of trouble in the sentences used initially is correct. In the way you seem feel more comfortable saying it, the word problem might be better suited.

Joe, while I agree with your assessment of the rule I disagree with the example with which you chose to break it. The exclamation is implied as part of the quoted word so in this case it would make sense to include it inside the quote marks.
The statement that includes the quote seems to beg for a period rather than a banger as in "blah!". This is of course incorrect in America, where it is perfectly acceptable to choose varied styles within one piece of text, unless it is for publication in a speciffic print vehicle (in which case their rules would be the best choice) the last punctuating period can also be implied by the close quote containing some other closing mark.
The art is to make up the rules in such a way that they do not disagree with your sentence.

Neither in this use refers to the implied word "choice" therefore is singular.

Rufus is right. Vid: This knife has dual purposes. This knife is dual purpose.
A knife of a different color. While potentially correct and illuminating IngisKahn's answer is reductio ad absurdam, and multipurpose knives are not under discussion. American English is a living language and what feels correct is generally acceptable, as long as subject, verb and object are in some semblence of harmony. I won't discuss British English.