One of my favorite GMail features is plus addressing [?]. I already, with my domain, hand out tons of aliases when signing up for things, and so being able to continue that method of tracking where an email address was harvested from is very useful.

Today I received five pieces of spam, all of them were sent to my gmail address without the trailing + part. Meaning, I believe, that spam harvesting spiders are smart enough to clip that little tag off before committing the address to their database. I don't believe I have ever placed my address on a spiderable page without some sort of + addressing tag.

Also, two web forms I have filled out in the past week have filtered the + in my gmail address as a space (which is understandable, it's a method of urlencoding spaces), rendering the account I was creating unusable.

I like the idea of plus addressing, but I am afraid it's not going to be as useful as I had hoped if spam harvesters are clever enough to know when they're being tricked, and web developers are filtering out the plus character in registration pages.