I have heard multiple times on channels (especially on Oasis) that there is no room for small guilds, that there are too many people who choose that rout and that they should be merged into larger guilds. I do not think any of that holds true. Smaller guilds have just as much value as larger guilds, and when they work towards a common goal pretty much anything can be accomplished.
Personally, I'm behind her 100%. Two of my three guilds are of the smaller/less-hardcore variety; my WoW guild is actually large enough to raid tougher content, but I don't think they would fall apart if that wasn't possible anymore. So who are these people who hate on the small guilds?
Too Many Guilds?
Feldon's got what seems to be a summary of the complaints in his treatise on EQ2 raid populations. Though SOE has exacerbated the situation with a debuff-curing-heavy raid game that is apparently contributing to healer burnout, the broader population issue applies to just about any game out there. Feldon's guild has 2/3 of a full raid force, and is one of "over 15 semi-casual raid guilds each about 4-8 players away from having a full raid force" on his server.
This leads to a frustrating situation, though I'm not sure it's entirely fair to dump it at the developers' feet; you could fix the debuff thing tomorrow and guilds with 16 raiders still won't (or at least shouldn't) be able to beat 24-man content. I think the point that people miss when they complain that there is "no room" for smaller guilds is that many of the people in those guilds are in a small guild for a reason, and, indeed, would not be welcome in larger, more dedicated raid forces.
(As if to prove this point, Feldon quotes a forum post by a raid leader complaining that he had only two applicants from a specific healing class over a three-month period, and that neither of them could hack it. Is it really a failing in the game's design that the few people who have the skills to heal top-end content and the desire to play high-demand, rare classes choose to join guilds that an actually field a full raid? I mean, yes, technically the holy trinity plus fixed group size are design decisions, but that's not some minor balance issue or content design priority that you can fix with minor tweaks to a launched game.)
Different Solutions for Different Priorities
The bottom line is that the types of guild group you form are going to depend on your goals. If running the latest, fanciest full-group raid is a priority for you, then you should be looking for a guild that can accomplish that goal (and you should probably either be in the top tier of your DPS class or a healer, since most guilds have the requisite 1-2 tanks and at-least-average DPS). If you're going to have fun doing whatever happens to be going on, whether it's at level 20 or level 200, and your small guild supports that goal, there's no fundamental reason why you should have to change.