The pump and dump scheme, whereby someone pushes rumours of a penny stock’s inevitable rise, have been around for a long time. Someone with a huge pile of the junk stock floats the rumours. When the suckers buy in, they are picking up the stock the fraudster owned.
Spammers are no neophytes to the pump and dump, right along with their fax spamming colleagues. But everyone gets tired of a pitch now and then, so spammers turn off the spigot every so often.
It has just been turned back on.