Bukkit

The block trails are interesting, but unusable in a practical sense.

The blocks push your around because they are placed on you, and they stay forever, so people could just farm and dupe with the trails.

How I imagine they could work is, the block is placed under the feet of the player, replacing any block they are standing on, and disappear after a few seconds.

Plugins like Magic Spells and Red Carpet and stuff, have similar effects though not nearly as customizable as yours, and there is no exploiting with spawning blocks etc.

For instance, it would be great to give really high donors, the ability to walk on blocks of diamond. These blocks wouldn't be harvest-able because they aren't really there, and they disappear shortly after appearing, basically making it look like they are walking on diamond all the time, but without the side-effect of mass spawning diamond blocks and flooding the economy etc lol.