A recent discussion on the WSPRnet website concerns whether one should log WSPR contacts. It was pointed out that normal WSPR "spots" are not contacts. However it appears that some operators consider that if two stations spot each others' signals within a short interval of time then they treat it as a contact and QSL it.
In my opinion WSPR spots, even if they occur both ways within a short time, are not contacts because you have no way of knowing if someone else received your transmission (or what signal report you got) without using the internet. It would be nice if the WSPR protocol provided a way to discover who is hearing your signals without using the internet but it doesn't. I have no issue with QSLing WSPR "spots" as SWL reports. But they are not contacts, and if anyone uses eQSL to send a QSL to me for a WSPR spot it will be rejected as "not in log."