Future Paradoxes

Ive been paranoid for the past few years of time travel.
Now i know i deal with 'Theoretical' bollocks, but if for some strange possibility it does happen we as a people must be prepared. Why?

Image a distant relative from the future comes to the present.
Now here' hoping that in the future, people are wiser, smarter, and far more logical that they would go back to the past to 'examine' and 'observe'.
But as time progresses, it would be an everymans vacation deal.
The average person, less in the skills of reason, can screw up the past and erasing the present future. Can this happen? Lets take a look at history shall we?

Cars: only skilled engineers were allowed to drive these vehicles that ushered the 20th century, now every spoiled 16 year old with a inheritance can plow into you because of a cellphone argument and light drinking.

Air-Planes: only the rich elite were able to fly in one of these, and even then, there was a code of conduct and process to allow a passenger in. Now, it is a terrorists ultimate weapon.

Internet: originaly used for scientists and doctors to pass on information to help save lives or push the boundaries of knowlege. Now is used to push the boundaries of Vices and created a new breed of perverts and child molesters.

The list goes on and on.
but now that i think about it, how many times has our 'present' been altered?
is there a way to monitor the time paradoxes?
The fabric of reality can only handle so much. We're already over populated as it is, all we need now is a future lonly man to go to the past for vacationing like most people here in the present visit Thailand for vacationing. There going to be screwing the gene pool.