Oliver said

Who turns violin pages in an orchestra? (Sometimes piano guys have a helper but I think piano players turn pages better anyhow without help.)
Do people ever share a stand? Who turns pages?
Is there an accepted height for a music stand (and the music it will support) ? Is the top of the score at eye level?

As Ken said, there are 2 players per stand in the string sections and most often the player on the inside turns. Left for violinists and right for violas, cellos and basses. Fact of the matter is that it's closer for the guy on the right to get to the page but both tradition and the fact that the audience can see the outside players thus looks better to see them playing continuously. Even though for concerts the outside player usually turns, it's common for even outside players to be kind and turn first so to speak out of respect for the other guy......
Since many orchestras rotate now a days, except for the first 2 or 3 stands, everyone gets a chance to be the page turner except primary concert masters and section leaders.

As far as stand height is concerned, it differs from player to player. I like to have it low so I can have contact with other sections in the orchestra. Many people are so glued to their parts that they need to have it high be able to see the conductor in their peripheral vision. I also think it's nice for the audience to be able to see the players rather than the music stand.