The main stylistic argument against the use of parentheses in a paper title is that parentheses are an expository device that should be used very sparingly, even in the body of a paper or other text. I learned this the hard way: for many years I had a bad habit of injecting too many parenthetical clauses into my writing. At some point I became aware of this and started making a conscious effort to replace any use of parentheses with an equivalent non-parenthetical statement, and found that in 90% of the cases doing so made sense, was easy to achieve, and improved the presentation. Overall I feel that my writing has greatly improved thanks to this small change, and I would recommend to anybody to follow the same guideline that parentheses are like a strong spice, to be used in moderation and only when there is a very good reason to do so.
With that said, I have used parentheses in the title of one of my own papers (the idea of one of my coauthors, but not necessarily a bad one), and think that this is fine if it serves some clear purpose and done in good taste. As others have commented, it may be done to lend the title a slightly more informal feel, or to inject a pun or a bit of humor, or to add some important qualifier to the main statement of the title, e.g., "The infinite-dimensional halting problem is (almost) undecidable."
Finally, I do think using parentheses at the beginning of the title is almost certainly a very bad idea. Parentheses by their nature are just a little bit distracting, and the beginning of the title of your paper is the last place where you want to distract your reader's attention. The title should have a strong, punchy start that pushes the reader along and helps them to appreciate what your paper is about; see a related discussion here. Moreover, another small principle of good scientific writing is that sentences in general, and titles in particular, should not start with punctuation marks of any sort (or with mathematical symbols), so that's another reason why parentheses would be bad at the beginning of the title.