Xmarks had lots of users but little engagement. Apparently it forgot to figure out what the users needed or wanted.
“For the popular bookmark syncing service Xmarks, 2 million users was apparently not popular enough. Co-founder and CTO Todd Agulnick announced on the company blog Tuesday that, despite growing by 3,000 users each day, the startup was floundering and would shut down its service in 90 days….
Unfortunately, users who tried the system were looking for answers to questions rather than topical lists of sites.”