I like the use of painters tape (I recycle what I receive), but some do a bit of overkill. Protection is vital, but sometimes just getting the tape to start peeling off requires a fingernail dig. I try to use small pieces, with an edge folded back for the recipient to to get an easy start on pulling it off. On a similar note, if you are surrounding your cards in (Cereal box for example) cardboard, leave gloosy, printed side outside. The tape peels more cleanly off of it (for reuse), while the unglossed side stickes more to tape, and bends sometimes when peeling tape off. Sorry to sounds so anal about this, but just things I have noticed.
Also, I use a lot of photo mailers and know they can be tough to open, but seem to protect well. To any who receive them from me, I suggest cutting down the right or left edge, just enough to open one end of the envelope, then sliding cards out. I leave buffer at all edges, so if you cut a 1/32 or so you will be safe.
"He stood there like the house by the side of the road, and watched that one go by." - Ernie Harwell