This is definitely convenient for now, but the shifting browser ecosystem (along with default security changes in Safari and proposed changes in Chrome) is driving the development and adoption of server-side tracking solutions. This is great for the short-term, but I imagine it won't be relevant much longer.

There's a reason why Segment just sold for $3.2 billion... [edited to add: They offer a single integration point and will proxy your data server-side to hundreds of other companies.]