BoingBoing links to an interesting story about time travel and a self-policing community of time-travelers (modeled on a Wiki community).

11/21/2104
At 02:21:30, SneakyPete wrote:
Vienna, 1907: after numerous attempts, have infiltrated the Academy of
Fine Arts and facilitated Adolf Hitler’s admission to that institution.
Goodbye, Hitler the dictator; hello, Hitler the modestly successful
landscape artist! Brought back a few of his paintings as well, any
buyers?

At 02:29:17, SilverFox316 wrote:
All right; that’s it. Having just returned from 1907 Vienna where I
secured the expulsion of Hitler from the Academy by means of an
elaborate prank involving the Prefect, a goat, and a substantial
quantity of olive oil, I now turn my attention to our newer brethren,
who, despite rules to the contrary, seem to have no intention of
reading Bulletin 1147 (nor its Addendum, Alternate Means of Subverting
the Hitlerian Destiny, and here I’m looking at you, SneakyPete). Permit
me to sum it up and save you the trouble: no Hitler means no Third
Reich, no World War II, no rocketry programs, no electronics, no
computers, no time travel. Get the picture?

At 02:29:49, SilverFox316 wrote:
PS to SneakyPete: your Hitler paintings aren’t worth anything, schmuck,
since you probably brought them directly here from 1907, which means
the paint’s still fresh. Freaking n00b.

At 07:55:03, BarracksRoomLawyer wrote:
Amen, SilverFox316. Although, point of order, issues relating to early
1900s Vienna should really go in that forum, not here. This has been a
recurring problem on this forum.