I agree GenesReunited are useful. I came across one or two family lines from distant relatives I met on GR. But I think these days there is quite some competition for the loyalty of genealogists and you may need to pay the sub and proactively look for connections, rather than waiting for people to find you.
All the same, at least two of my 'leads' on GR turned out to be false - they had jumped to incorrect conclusions or copied incorrect information from someone else. You really need to check the information yourself if you want to be sure you have the correct facts.
In reality, distant connections can come from all sorts of unexpected directions. I bumped into a distant cousin in a local history museum by chance and she subsequently sent me 8 pages of family trees from the C17th to the present day!