I wonder about that every few months and then as soon as I see a scraper or spammer using my company name in yet another TLD I wonder why I didn't buy that one.
Only this week I've seen a scraper site who'd registered my .pro gTLD spamming themselves to the top of the SERPs in just a few weeks.
Anyone within my industry who looked at that site would know immediately that it's not mine and that the content is garbage therefore not much damage has actually been done but it's just annoying me that I didn't register it before him and even more annoyingly I had been thinking about it for a year or so!
My feeling is that it is probably an unnecessary expenditure.
It's a 100% valid tax deductible expenditure insofar as I am concerned in the UK, therefore if you are in the position of paying company/personal taxation, it becomes a moot point in most jurisdictions I would have thought?