Ancestry recently made an update to their DNA functionality (or I just noticed it, not sure which). If you've taken an AncestryDNA test and haven't checked your Member Match results lately, they have begun to add the "shakey leaf" to matches that have common ancestors. This feature identified several cousins where we share a common ancestor at the 4th-great-grandparent level, one where we share a 5th-great-grandparent and another at the 6th-great-grandparent level. Pretty cool!
There are still many potential connections who have no family tree connected to their results. Perhaps as more people become aware of the possibility to more easily identify common ancestors, they may connect their trees to the DNA results.
It has been cool to find the connections have been on both sides of my tree. We have the additional information from my Mom's results and that helps quite a bit too. One connection appears to have a link somewhere in the tree from my Granny's Hermosillo, Sonora line, which is a part of the tree where I have a brick wall with my 2nd-great-grandfather Manuel Portillo. More research is needed, but the DNA results are beginning to pay off by identifying others searching for the same families.