Not knowing much about think tanks, Wikipedia sites Brookings as the most frequently cited source in the USA, so I pulled up their job board. Not many openings in research- a lot of support positions though. Most of the jobs required a bachelors, but of the ones that wanted PhD, they were looking for previous academic research experience in a big way. I think being an enrolling in a PhD for the purpose of being an aspiring think tank member is less likely than landing a tenure position. There aren't even that many think tanks. https://careers-brookings.icims.com/jobs/search?ss=1&hashed=-435682078
Brookings is just one organization. I wouldn't base my opinion of an entire industry on one organization.
Yes, but in Canada there are not so many online PhD programs but numbers are similar due to several reasons such as budget cuts, less need of university educated people and proliferation of online courses. Many schools are finding out that teaching online is also an excellent way to reduce full time positions. One part time teacher can teach 300 hundred students online. Few schools in Canada are growing because the use of online courses. Full time faculty is expensive, hard to fire, difficult to train, ask for benefits and requires office space. Part time online faculty do not need office space, do not require benefits and can be laid off when there is no longer need for their skills and replace with new faculty with new skills needed. The future of faculty in my opinion is many part time faculty teaching online classes. People are still willing to complete doctorates for an online adjunct career so why schools should give them full time positions with benefits. I worked for few school such as Walden and Devry that rely heavily on adjuncts, many adjuncts take administration roles with the school as faculty managers, course developers, etc and become almost full time employees but without the benefits, pension plan, etc. When I started as an adjunct, a Masters degree was fine but now the PhD has become the bear minimum requirement at some schools while others are started to ask for adjuncts with publications mainly to target accreditation such as AACSB. I see people often now with two doctorates, this was very rare before but now it seems that online has made it easier for people to get a DBA or EdD on top of a PhD. If you search in linked in, you will see quite a few people with double doctorates from place like Capella, NCU, etc. Credential inflation is here to stay.
It's been identified as an issue for 45 years: http://www.amazon.com/Diplomaism-David-Hapgood/dp/0878690026/ref=sr_1_1?ie=UTF8&qid=1462545317&sr=8-1&keywords=diplomaism
