This is probably good to avoid general low-hanging-fruit spam, but anyone who spends even a second manually configuring something to spam your exact site will be able to get past this with extreme ease.
So for most sites, it'd probably be a good idea to put things like this in place but then to also be ready to roll out reCAPTCHA at any given moment, in the event a serious spam campaign begins.
So for most sites, it'd probably be a good idea to put things like this in place but then to also be ready to roll out reCAPTCHA at any given moment, in the event a serious spam campaign begins.