I find it frustrating that we can't build smart lists off of Marketo IDs. I frequently need to be able to build a list off of Marketo IDs and no other field will suffice. I have this problem right now and have no idea how to workaround it.
For us, email addresses are NOT unique, and do not work as a searchable field. Best practices or not, we work with agents who represent different buyers, and so the agents' email addresses will show up multiple times in the database, but for different accounts, i.e. different Marketo ID entries. Running lists off of email addresses will pull the wrong people, or only the first instance of that email address. Additionally, some people won't have email addresses, so we can't always search/build lists off of email addresses anyway.
What is the reasoning for this field not being available? I've seen from multiple discussions that other users want this functionality as well.