First and absolutely foremost Linden Labs needs to LISTEN. For years now people have over and over been stating what Linden Labs needs to do, but, the attitude of the lab more and more seems to think people are unaware of their behind the scenes issues and concerns. I'll give a few examples:
1) Land. Prices are too high. A few land "barons" get the best deals and squeeze out anyone else trying to compete. If Linden Labs wants MORE people, why do they favor a system that creates a few successful folks who then force everyone else out. This also then continues to allow other start up grids to under price them and seem far more appealing to new "customers" just entering?
2) Content creators. Why continue to allow rampant theft of intellectual property and make preventing such theft almost impossible for merchants to stop. A system can and should be in place to make it EASIER to report copying and quicker to get copies pulled. The lab should aggressively pursue and shut down rogue programs that make copying easy and make it clear to those stealing the property of merchants that they are not welcome in Second Life. Instead, the opposite is true. Merchants feel Linden Labs makes it as hard as possible to file DMCAs, offers no assistance, and does the bare minimum required by law and only when pushed into doing so. Good content creators continue to leave Second Life, reducing the amount of good content here and making the grid less and less interesting to new arrivals.
3) Greet new arrivals and make them feel welcome. Fill the welcome areas with posters and landmarks of all that there is to do in Second Life. Have people available there to help. Get rid of those who just look to troll, attack, and laugh at the "noobs" first coming in to see what Second Life is like.
4) Get rid of all that mainland sitting unused and empty. Reduce the number of mainland continents. No one wants to be in a world that feels like an abandoned and empty wasteland (well unless you're role playing that kinda thing). Make it easier to report land abuse and quicker to resolve such issues.
5) Adult themes. There should be a time and place for everything... and every place isn't right for adult themes. New people coming to Second Life continue to feel everyone here is a pervert or sex addict. Try coming into a welcome area with a female AV and see how long it is before someone asks you to role play virtual sex with them. Crack down and make it clear such behavior isn't welcome everywhere in Second Life.
6) Stop forcing people to accept what they don't need or want. Search has changed now to where no one can use it to find anything. Viewer two was universally rejected as decidedly non-useable. Mesh is not needed as a replacement to sculpties. Direct Delivery is only going to create more problems as it continues to overload the server to replace a system that should have been fixed instead of replaced.
7) Someone once said businesses should take care of their customers... and when they do their customers will take care of the business' profits. Linden Labs should take a step back and try to understand that mentality... instead of seeing their customer demands as a drag on profits.
Hope this helps, but, sadly I'm sure it's only going to attract those who will point out I'm not helping or understanding of the Labs issues.