Well, I would highly recommend some sort of reliable ID on the cattle. Branding is of course the most reliable and permanent. Properly applied ear tags are pretty good, but IMO should include more than just a # on them. You can add your name, phone #, etc to them. We just add our Brand to the top front of the tag, some sort of info should be on the front, just for easy identification. Use the back for more in depth stuff like your phone #. Another option is metal ear tags (Kurl-Lock) They are pretty permanent, and you can have your name stamped into them, as well as numbers.
Some sort of ID is good, not just because someone might try to steal your cattle (not that likely, but possible) but because your cattle might get out, or mixed up with someone else's cattle. No ID makes it hard for you to prove the cattle are yours.... And makes it harder to sort different owners.
Here's a couple stories.....
We had a calf show up in our pasture late one summer. Had an ear tag, and we tried numerous times to find the owner. Couldn't see a brand on it, and in the end we did finally put it down the chute and it had no brand. The tag did have some info on it, but not a lot, in the end we wintered it and sold it with our own, never did figure out the owner.
A friend of ours had a cow show up in his pasture (2 hours from his home), he ended up bringing her home in the fall. No tags or anything, using the brand on it, they tracked it down to his next door neighbour. Turned out that the cow had been sold a few years previous, and the new owner had never put any ID on the cow. Can't remember if they ever figured out where she came from.