What's the line between salsa and guacamole?

Part of the problem is that "salsa" doesn't mean just one thing to everyone. If you do a web search for "avocado salsa" you get images ranging from liquid to chunky:

Similarly, there's no one "correct" way to make guacamole. Some people like it smooth and thick - hummus-like, if you will, other people like it partially mashed and partially chunky... almost the same as the chunky-style salsa.

So, how do we set limits if the products are so varied?

We really can't. I could write long "definitions" claiming that guacamole should be X% avocado and must be mashed in an authentic molcajete rather than in chunks or pureed... that salsas should be X% or less avocado and must contain things like tomato, onion, tomatillo... but you'll always be able to find something that calls itself "salsa" but seems more like "guacamole" or the other way around.

The important thing is, it's all delicious. Enjoy it!

The other part of your problem is that guacamole is a kind of salsa. From Wikipedia:

Salsa is the Spanish, Italian, Greek and Turkish (salça) term for sauce, and in English-speaking countries usually refers to the sauces typical of Mexican cuisine known as salsas picantes, particularly those used as dips. Salsa, contrary to common belief, is in fact not a condiment, although it may be used to flavor various food items.

Salsa is often a tomato-based sauce or dip that is a heterogeneous mixture that includes additional ingredients such as onions, chilies, beans, corn, and various spices. It is typically piquant, ranging from mild to extremely hot.

If you look under the "types", you will find guacamole.

Guacamole is thicker than a sauce and generally used as a dip; it refers to any sauce where the main ingredient is avocado.

You'll also find "Creamy avocado salsa".

Creamy avocado salsa is a sauce made from avocado, lime, cilantro, jalapeño or serrano peppers, garlic, olive oil, cumin, and salt.

Still, they're both "salsas".

So, in the end, there is no way to separate the two... though, if I were at a restaurant and order "guacamole" and they give me the first image at the top... I'd complain. Any of the other three, I'll take.

I think what you are seeing is marketing speak. Many different manufacturers put out similar products but may call them by different names. From what I've seen, guacamole, guacamole dip, and avocado dip are pretty much synonymous. They can all be used as a dip or condiment.

There will be differences, e.g. one may taste slightly different than another or one may be chunky and another smooth, but the manufacturer chooses what name they give it from a marketing standpoint.

Regarding a line between salsa and guacamole, I don't see that there is really a line. What I mean is, adding avocado to a salsa doesn't make it guacamole any more than adding apples to a salad makes it a Waldorf salad.

The traditional guacamole is a salsa made specifically from avocado (the word comes from Nahuatl "ahuacatl" - avocado + "mole" - sauce).

So your Venn diagram would have guacamole inside salsa. Once you start omitting the avocado in your salsa, you've left guacamole-land.