I would say before we are dealing thousands of microtransactions per day, which I still consider to be far off, is the idea of people and corporations using vanity addresses. Let's just say that I want all my addresses to start with Mark (or as close to mark as possible, e.g. for bitcoin would be 1mark and for litecoin would be Lmark and so on).
Since there is no way to start with an address including, say 1mark, and reverse to find the private key (an assumption on which mining, password hashing, and many other security protocols are based on); I will have to do the inverse: generate a random private key, create a public key, and check if this public key meets my criteria. If the address I generated starts with 1mark then I will add it to my wallet, otherwise I will throw out this private key and try again until I find my address.
Bitcoin and it's derivatives do not allow certain characters in public keys as to avoid confusion. I believe these restricted characters are: number 0 and capital O, number 1 and lowercase l (except for the first character in a coin address). This means that I have 58 usable characters (26 UPPERCASE letters + 26 lowercase letters + 10 numbers - 4 unusable characters in these sets). I do not believe there are more but someone please correct me if I am wrong :)
If there are 58 usable characters for an address, and let's say I am very concerned about the capitalization of my name (i.e. it needs to be 1mark, not 1MaRK or any other permutation with capitalization), the average amount of addresses I will need to generate to find an address begining in 1mark would be 58^4, or 11,316,496. If I didn't care about the capitalizataion of my name it could be as low as 707,281 addresses generated to find an address which begins with my name. That being said, I have a pretty short name, someone name Satoshi will need many more hashes to get his name as a vanity address.
If the water company is using vanity addresses as well, (e.g. 1water) to help their customers differentiate their charges or for any other reason, this increases by the amount of vanity addresses they use per day.
I would use a vanity address generator (see disclaimer) to do this currently, I imagine it will likely built in to standard wallet software at some point, since it is a nice novel feature and allows for more custom firstbits (short identifiers for bitcoin addresses, more information on firstbits can be found here https://en.bitcoin.it/wiki/Firstbits ).
Disclaimer: be careful how you generate a vanity address, currently the best method is to use VanityGen (more info here: https://en.bitcoin.it/wiki/Vanitygen ). Please read up on the possible issues with a vanity address generator and make sure to do so securely if you intend to use a vanity address to save any significant amount of coins (e.g. make sure that the developer can not get access to your private key during or after creation, by running vanitygen on a live usb without connecting to the internet).