I saw many sites that using the on their domain ranks well on Google search result, so there is no bad effect on it
using "the" would have no significance as long as you do your SEO work. Most people do not appreciate the presence of "the" for reason that in keyword domains, the keyword part usually comes after "the" rather than as the first word.
It will significantly reduce the value of the name. As mentioned, it makes it longer & also harder for people to remember. What would you rather owning, Cars.com of TheCars.com?
Using The in the domain name is not bad. However, the keywords you try to rank for should be at the beginning of your domain name, for best results. So for example: CarWhatever.com is better than WhateverCar.com if you try to rank for Car
I think it depends on the domain also..for example, the makes sense if you want people to use it as your brand..for e.g the planet, the incredibles etc..otherwise, it makes no sense by adding a 'the' since you will be just making the name bigger and difficult to remember ..
It looks cheap to me but it could work in a few situations where it sounded good. The other one I dont like but always see is "my" ... bah humbug on that one too!
Unless it's something like TheMan.com or TheBigDog.com (whoever owns them)... You need unique variations to the 'the' prefix stand out to surfers.