I seriously have no interest in judging the Mendeley folks. I still like them, and who am I to judge? If someone offered me $45M (the minimum estimate that I’ve seen) for a company I built from nothing, and especially if the acquiring company assured me that it would preserve the values of that company, I might well take the money. My judgment is actually on myself. My faith in the ability of well-intentioned private companies to withstand the brute force of money has been shaken. After all this time, I was foolish to have believed otherwise.
It’s best not to rely too much on any vendor of any service – you never know what might happen. Doesn’t mean you shouldn’t use them, but have a backup plan and keep a hold of your data.