I’ve always hated the target blank feature. Whenever I click a link that unintentionally opens in a new tab, it feels like an intrusion on my liberty to interact like I wish to, and even feels like my browser is taken as a hostage. Ok, it sounds as an overkill to put it that way, but users actually can open links in new tabs ; target blanks just remove the choice to do so. The worst are links of the same domain that open in a new tab (luckily, it’s very rare). In any case, target blank links can end up populating your browser with dozens of unnecessary tabs.
The reasoning being implementing them is to prevent the user from leaving your site. Actually, the user does leave your site, but you hope that, while closing tabs and eventually stumbling again upon your site left in an inactive but open tab, the user will eventually resume his browsing or at least remember where he initially came from.
Most users probably do the same thing as me: close this tab we’ve forgotten about and just move on. So, does the target blank fail to fulfill its sole objective? Not really. Leaving a tab inactive but open probably still counts as a visitor present on your site, and will show as such in any implemented analytics script. And I guess ‘Visit duration’ can act as an interesting leverage in any advertisement-focused decision.